Great design, perfect size, beautiful solution - no wonder Cast Chain is one of my favorite 3D puzzles. It consists of 3 chain links, labeled with 1/2/3 dots, which are connected to each other. The links are made of rougher metal, which contributes a lot to the overall appeal. The reason I like this toy so much is the elegant solution it offers. It is smooth to manipulate and fun to play with. Cast Chain is one of the top puzzles by Hanayama and highly recommended.