In general, the Gears line is a great STEM toy, but this is a poor set. There are very few pieces in this set by comparison to others. The springs are fun, but hard for little hands to remove or move. My son always asks for help with them. The propeller was the one great piece in this set except it was broken on arrival. Customer service was poor. They promised to find a replacement propeller but never never called back. Hubby fixed it with a fiberglass kit.