I bought this for my 6 year old son as a replacement for another Christmas present that didn't work. Great set full of things to build and just about the right level of difficulty. Some quite taxing things to create, but he loves building all the different models and likes the roaring noises too. They don't include the instructions for all 20 models in the set believe it or not, just the simpler ones. So if you want to build the more complex models you need to download these off the internet. There's lots of pages to print out, so that's a mark down on this set's rating but in all other respects it is very good and, for Knex, quite good value for money, which is not a phrase I'd often use for Knex stuff !