Gear Shift _ Meffert's Twist and Turn Puzzle _ Bonus Twisted Nails Puzzle Fantastic gear based twist and turn puzzle. Easy to mix up colors. Objective: After thoroughly mixing colors return puzzle so there is a single color on each side and a perfect cube. Puzzle halves actually pulls apart by about 1/2 inch making the twist action even more crazy. Four gears on one side can turn independently when puzzles halves are pulled apart. Recommended for ages 10 to 105 years. Bonus: Twisted Nails Puzzle. Separate and then rejoin the 2 carpenter's metal nails.