The most used toys in our house are the duplo blocks aka the larger lego blocks. My five year old builds all kinds of machines, characters, and places with his blocks that he then pretends and creates his own imaginative world. He would often build ramps and slide many unsuspecting toys down. I wanted to add to his ability to create something that could create a track or a path that objects could move on. These marble run building blocks are perfect. This set gave my husband and two boys an activity they enjoy working on together. They have built the three different tracks that the instructions describe, and our five year old has created his own variations. These blocks can be used with his original duplo blocks, so, he can make his creations even more elaborate. The only downside is our two year old likes to send the balls to their death under the oven. Nothing a a coat hanger can't fix. So, if you are looking for a new toy that will be used and used again for years to come, I recommend these marble run building blocks. The link provided goes to the set I originally bought that is seen here in the photos, but it is currently unavailable, but many alternative block sets will show up as suggestions when you follow the link. Let me know what set you try out and what your kiddos think. Enjoy!