Bits and Pieces - Black/Silver Yin and Yang Metal Brainteaser Puzzle-Metal Puzzle Brainteaser, Nickel-Plated - Measures 2-1/2" in diameter It may take an infinite amount of time to solve this mind-boggling metal brainteaser by designer Doug Engel. A great gift for people who love brainteasers and trick puzzles. Will you be the one to unravel the mystery? Try to take the four nickel-plated pieces apart then fit them back together. 2-1/2" in diameter. Solution included.