Review on ROKR Self Assembly Educational Engineering Grandfather: Building Genius and Fun in One! by Roberto Manzer

I made 6 of these sets and this one was the most fun. The quality and ease of assembly of Rokor are fully coordinated. I helped my brother-in-law with this - his first. He smiled the whole time. Took about 8-9 hours over three days. The quality and accuracy were amazing. If you follow the instructions very carefully - invent and smooth the edges of all gears three times, it will work. Lots of wows and smiles as the spring was wound and the whole thing flew across the floor. A wind gives you about 8-10 feet. I would call this a mid-range kit.