The Luban Puzzle is also named as Interlock Puzzle. Based on the principle of the eight-diagram metaphysics, the concave and convex parts inside the three-dimensional interpolation toy, mesh perfectly. Luban Locks come in different shapes and sizes, with different internal structures. But they are usually easy to take apart but challenging to re-assemble. Each piece is approximately 3.5cm and weighs approximately 20g. This Luban IQ Puzzle is made from plastic and a great toy to keep bored kids on their toes as they challenge themselves to pull apart and put the pieces together again. Each pack Includes 12 pieces with assorted designs. Each luban is about 35 x 35 x 35 mm Age appropriate for 7 years old and up.