Cast Twist Metal Puzzle from Hanayama of Japan is a delightful and tricky brain teaser puzzle. It consists of a gold color and silver color ring The two are joined. The object is to separate the two pieces and then rejoin. Each piece has several strategically placed grooves circulating around. This is a really fascinating disentanglement brainteaser. You may find yourself totally immersed into how best separate the two halves. Recommended for ages 12 to 105 years. A few bright 7 to 11 year olds may also enjoy, provided they are aware that forcing the puzzle is NOT necessary and could destroy it. Rated by the manufacturer as a level 4 difficulty (on a scale of 1 to 6; where 6 is the most challenging.)