Introducing the K’Nex Building Sets – Things to consider before buying

By | January 9, 2015

In this article I want to give you an overview of the K’nex building sets and discuss some of the pros and cons. I will also take a look at some of the basic sets available and what age children they would be suitable for.

K'Nex model crane

A model from the 375-piece set

The K’Nex building sets are very different from building blocks like Lego and you can’t build solid walls with them. They consist mainly of a variety of plastic rods and connectors with a few other pieces like wheels and gears. These can be connected in many different ways to allow many different models to be built.

They have 2 ranges of building sets: one targeted at the consumer (that’s us) and one targeted for schools – the education range.

In addition to this there are 3 different size ranges: the K’Nex classic that I will be discussing here, the K’Nex micro that has pieces about half the size of the classics and the Kid K’Nex with larger pieces designed for small kids. The 3 different sizes do not work together, so keep an eye out for this when you are shopping.

The fact that these sets are used in the classroom already says a lot about their potential for helping children learn and develop important skills. The one area where they are used a lot is for teaching technology and engineering skills with sets such as the Real Bridge Building set. The education range covers all the STEM (Science, Technology, Engineering and Mathematics) areas of learning. I will discuss these in a separate article, but I wanted to show you that these building kits have many educational benefits. This is a good reason to encourage children to play with these types of toys.

The sets are meant to encourage open-ended creativity where children get to use their imagination to build their own creations and play with them. The model instructions included in the sets are meant to give examples of what can be built. Children can then modify these models and begin to develop their own designs.

The pieces are all color-coded. This makes it easier to find pieces that are the same and also to follow the pictorial instructions included in the set.

Let’s take a look at the basic (classic) sets in more detail.

To avoid repeating myself and telling you the same thing repeatedly for each set, I want to summarise some of the aspects that apply to all of the sets.

The manufacturer’s recommended age:

All of these sets have a suggested age range of 7 to 15 years. Feedback from customers on Amazon indicated that a 7 year old child struggled with these sets, but from 10 years up this was not a problem. The younger children needed help with figuring out how to connect the pieces and also with following the instructions. The older children coped a lot better.

The included instructions

Many people were disappointed with the instructions. They are not truly step by step instructions and take jumps from one stage of the creation to another, especially with the bigger models. Many of the younger children were frustrated by this and needed help to be able to build the models. It is easy to miss something and make a mistake and not so easy to spot the mistake until you are quite a bit further along with building it. The color-coding of the pieces is supposed to make it easier to follow along.

Now for some specifics of the basic sets

K'Nex 375

The K’Nex 375-piece set in a tub

K’Nex 375 Piece Deluxe Building Set

  • Number of pieces: 375 classic pieces, including wheels
  • Suggested Age: 7 – 15 (see notes above)
  • Building ideas included: 30
  • Storage tub: yes
  • Price range: From $12.93 to $19.99
  • Amazon average customer rating: 4.6 / 5

This is one of the smaller sets and is useful for building small models. For children that want to build large models they will find that they don’t have enough pieces, especially of the longer connectors. A good variety of models can be built, including a crane, a helicopter and a truck.

What people liked about this set:

  • The instructions include moving, interactive models.
  • The pieces are easy to snap together.
  • It kept the children busy for hours.
  • Encourages children to use their imagination.
  • The models are quite durable if they are put together properly and can be played with once built.
  • A set that can grow with the child as they build more complex models.
  • The plastic storage tub is good to keep the pieces in and big enough to add pieces from more sets.

What people did not like:

  • There are no instructions for some models shown on the box.
  • Larger models have a picture only and no step by step instructions.
  • Not enough pieces to build some of the larger models.
  • Instructions don’t give much detail for larger models. Just a picture and you have to figure out how to build it.
  • It is difficult for younger children and children with low fine motor skills to put the pieces together properly.

Overall this is a good beginner set if you don’t expect too much from it.

K'Nex 50-model set

The K’Nex 50-model set in a treasure chest

K’Nex Classics 50 Model Building Kit

  • Number of pieces: 700 classic pieces, including wheels
  • Suggested Age: 7 – 15 (see notes above on the appropriate age)
  • Building ideas included: 50
  • Storage tub: Chest-shaped cardboard box
  • Price range: From $58.95 to $64.41
  • Amazon average customer rating: 4.6 / 5

This set has more pieces, allowing larger models to be built. The building ideas include instructions for sea creatures, a hot air balloon and a sand castle.

The customer reviews on Amazon were mostly positive about this set.

What people liked:

  • A good variety of models can be built with the set, including taller structures such as windmills and buildings.
  • The box is quite big and can store incomplete models together with the pieces and instructions, keeping them out of the way until later.

There were very few complaints, here’s a summary of them:

  • There are no gears and other interesting items that would enable more building options.
  • Not enough building ideas included in the set (more can be downloaded).
  • One customer complained about the rods not being rigid enough to be able to build tall structures. I did not see any other complaints about this so I am not sure what to make of it.

Nobody mentioned the problem with the manufacturer recommending this from age 7 upwards, but I think the same applies as for the other sets.

This set offers good scope in the models that can be built and is definitely a step up from the 375 piece set.

K'Nex 521 piece set

521 mixed K’Nex pieces in a handy storage tub

K’Nex 521 Piece Building Set

  • Number of pieces: 521 pieces, a mixture of classic and micro K’Nex
  • Suggested Age: 7 – 15 (see notes above on the appropriate age)
  • Building ideas included: 35
  • Storage tub: yes
  • Price range: From $18.98 to $24.99
  • Amazon average customer rating: 4.1 / 5

This set had quite a lot of complaints about it, although a few customers were satisfied with their purchase.

What people did not like:

  • There is nothing on the packaging that tells you that both classic and micro pieces are included. Remember that these do not work together so this like getting 2 small sets, one of each size. This was an unpleasant surprise for most customers.
  • The storage tub is large and the pieces fit into the bottom 2 inches of the tub. They complained that it took up too much space for what it contained.

What people did like:

  • The storage tub is big enough to add pieces from other sets or to store small models.

I don’t like the idea that includes a mixture of incompatible pieces (classic and micro), so I will be giving this one a miss.

K'Nex 70 model set

Is this the best K’Nex starter set?

K’Nex 70 Model Building Kit

  • Number of pieces: 705 classic pieces
  • Suggested Age: 7 – 15 (see notes above on the appropriate age)
  • Building ideas included: 70
  • Storage tub: Chest-shaped cardboard box
  • Price range: From $29.75 to $44.99
  • Amazon average customer rating: 3.9 / 5

This set includes pieces to build a plane, animals, amusement park rides and trucks. It has almost the same number of pieces as the 50 model set and I am battling to find out exactly what the differences are (except perhaps more building ideas). It offers a good variety of building options and is liked for that reason.

This set had the same complaints as for the 50 model set: it was not suitable for younger children; there were not enough of the long rods and the instructions do not step you through the building.

Again the treasure-chest box is a lot bigger than it needs to be, but has space to add more pieces.

Again this set offers more scope than the 375-piece set and is a lower price than the 50-model set. Looks like a good option.

Which one would I choose?

Having looked at what these sets offer, the customer reviews and the price, I think the 70 model set is the best value for money as a K’Nex starter set. The 50 model set has almost as many pieces, but costs a lot more. It’s just a pity they don’t supply it in one of those nice plastic storage tubs.

Buy the 70-model set now

Do you agree with my choice, or would you choose a different set? I would love to hear your opinion, so please leave a comment below. If you found this article interesting, please share it with your friends.

Perhaps you would like to see a more specialized K’Nex building set – take a look at some of my other reviews like the Mini-Golf Building Set, the Exploring Machines Set or the biggest K’nex set of all – the GrandFather Clock.

30 thoughts on “Introducing the K’Nex Building Sets – Things to consider before buying

  1. Dan

    Aaah man, I miss playing with these things. So many hours of memories came flooding back. These toys are awsome, I have to-get a set for-my girls.

    1. Lesley Post author

      I am sure they will love it! I will be reviewing some other sets as well, so keep in touch.

  2. Chris

    Some of this stuff looks amazing. A great tool for youngsters to get hands on learning skills. Would you say it is a combination of Lego and the old Style Meccano? I had both when i was younger but this looks a lot better.



    1. Lesley Post author

      Maybe it can be compared to Meccano, but there is little similarity to Lego. It offers quite a different experience to both and helps build some really good skills.

  3. Ship

    My son loves his Lego’s he follows the step by step instructions and basically puts together the model. He has autism so he loves his instructions and knowing what he is building. As a parent I love having him play with the K’nex because they really don’t have set instructions and I want him to be more creative. He needs to work on his imagination and the K’nex lets him do that. Great article.

    1. Lesley Post author

      It’s good to hear that he is enjoying them. Which sets does he have?

  4. Peter

    Oh wow, your site is great, I wish I was a kid again! Why can’t the age range be 7 to 60? Haha. But seriously, I have lots of young kids in my family to buy pressies for and you’ve really inspired me, so keep up the good work!

    1. Lesley Post author

      Well, the only reason for the upper age limit is to give an idea of the complexity. There is Robertson why you can’t enjoy them too. Let me know if there any sets that you want me to find out about for you.

  5. Mustardamus

    Thanks for the clear and detailed review. I will consider buying the 70 model set to my son.
    Do they have models with engines?

    1. Lesley Post author

      There is a car set with a pull-back motor, not sure of engines as such. Will be reviewing the car set soon. I will scout around and see if there are sets with an engine.

  6. Paul

    Great information! good timing too, I was looking to move my 7 year old son on from Lego to K’nex. Wasn’t too sure it could be a little too complicated for him, but as I still like to fiddle with Lego too i’m sure I can have as much fun with K’nex!

    1. Lesley Post author

      Thanks for stopping by. I am sure your son will love K’nex. Kids tend to love anything that they can show off their creativity with. Let me know which set you get for him and what his reaction was.

  7. Benjamin

    Hi there,

    I’ve used K’Nex before as a child and looking at them now I remember why I wasn’t impressed and stuck to Lego’s. Lego’s are the best toy building sets that have ever been invented. To be honest, the most learning to build and create things as a child will come from using whatever is available though. So while I’m pro Lego’s, I’m more for using straight intelligence to create with whatever is available.


    1. Lesley Post author

      Hi Benjamin,

      I agree that K’Nex and Lego are very different. This is also the reason why I like to have different types of building sets for my kids. The K’Nex range offers a very different building experience from Legos and different projects.

  8. Kasun

    Thank you very much for sharing these information friend. I have never heard any building set like this. I happened to know only about the building sets which can build solid walls and cubes. But definitely these seems to be more complicated and creative. This is really a Nice product.

    1. Lesley Post author

      The K’Nex building sets are a great change form the usual brick building sets. they are not complicated to use, but some really good, complex and fun structures can be built with them.

  9. Hostelgirl

    As someone who has worked in schools and preschools, I can agree that construction toys are a fantastic aid to creativity as well as problem solving. Who would have thought an educational toy could be so much fun?

    It’s good to have your reviews on there because often these things look the business in the packaging but then you find out you need all kinds of connecting bits. Thanks for the age recommendations too.

    1. Lesley Post author

      I think it is great that children can have fun and not even realize that they are learning good concepts and valuable skills. Usually all the pieces you need to build the models shown on the box and on the included instructions are included in the package. I have not heard of many people complaining about missing pieces, so this is not likely to be an issue.

  10. Kellie

    Thank you for putting these reviews together. I have a 5 year old grandson and never sure if I need to stick to the exact age recommendations now that he is out of the toddler stage. I know chewing on the toys is no longer an issue.

    What do you recommend? Do you think the Knex for 7 plus will be okay for him?

    I appreciate your input.

    1. Lesley Post author

      Hi Kellie,

      This is quite a difficult question to answer without knowing your grandson. The standard K’Nex pieces can be quite difficult for little hands to clip together and take apart. Depending on his strength he might need help from an older person.

      On the other hand, they will last him a lot longer than the K’Nex Junior range will and there are more sets available that will work with the standard ones. Take for example the Simple Machines sets that will help him later with school topics and projects – he will be able to build bigger models if he already has the standard sets in his collection.

      The Junior range has larger, softer pieces specially designed for little hands. These do not work with the standard sets and will be outgrown quite quickly.

      This is not a direct answer, but I hope it helps you to make a decision.

  11. purple rose

    I remember using something similar when i was young. Although my son still has many years to reach to this level I’m already excited about it. These sets are definitely more “sophisticated” than what i had on hand. I really hope my son develops a mechanical touch and has interest in building toys like these.

    1. Lesley Post author

      Children love the satisfaction of creating something so I think your son will love these even if he doesn’t develop a “mechanical touch”. the sense of achievement when they successfully build something goes a long way to help develop their self confidence too.

      Introduce sets that fit in with what he does like and you will be able to develop his interest in creative projects.

  12. Stephanie

    Hi Lesley:

    The K’Nex Building Sets sound like really awesome toys to get for children to help build imagination, creativity, innovation and have fun while doing it. One of my friends is a Civil Engineer and he started out playing with toys just like this when he was little. They were his inspiration in becoming an engineer. He learned that he loved to build things and developed his sense of ingenuity and vision for things through playing with toys just like K’Nex Building Sets.

    As a teacher, I recommend that every classroom have a building and construction set just like this one, because of the awesome educational benefits that can be had from this. The fine motor skills can help children as well as increase their analytical skill building.

    For parents, this would be an awesome holiday gift. This was a great review with loads of detail and information to help make a decision to purchase a K’Nex Building Sets for the kids in our lives.

    1. Lesley Post author

      Hi Stephanie, thanks for stopping by.

      It’s great to get an honest opinion from a teacher. My son loves building things and not only with construction sets. I am needing to get bigger sets for him to be able to have more of a challenge and be able to stretch his imagination a little. I will be surprised if he does not one day study for some type of engineering field.

      As you said, these sets are great in the classroom and also to keep the kids busy with something constructive in the holidays.

  13. allis

    My son would love building pulleys, elevators, and other machines but also any kind of vehicle. can we build such machines with the K’Nex 70 Model Building Kit? Or would we need the machine set? (that one is so expensive and my son is only 5- but really good at building) on the other hand i am worried he won’t like it if he cannot build machines. Any advice?

    1. Lesley Post author

      The 70-piece set does not come with any gears. It is a great set and will give your son a lot of building ideas. You can always add a set with gears at a later stage – take a look at my post about the simple machines sets.
      The link that follows is for the instructions for this set and includes a list of parts so that you can see exactly what you will get.
      I hope this helps.

  14. Jessica Roderick Katz

    How do you know what size you are getting? I don’t see micro etc on packages?

    1. Lesley Post author

      Hi Jessica, thanks for stopping by.
      This was the complaint a customer had about the K’Nex 521 piece set. It contains a mixture of classic and Micro-K’Nex pieces and this is not specified on the package. I have not come across another general set that has this problem. The Micro sets are usually labelled as K’Nex Micro and the Kid K’Nex are clearly labelled. The classic sets don’t have a specific label and most of the sets fit into this category.

  15. Marla

    What Knex set would you recommend for a 13 year old whol has a lot of knex but would love to add on to his collection in order to build more complicated things.

    Thank you

    1. Lesley Post author

      HI, I think this will depend on your budget. My first choice would be the K’Nex Classics 50 model building set. It comes with a lot of pieces and the set includes wheels. It will give a lot of building options.


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