Size: 47*7*7CM/group (four groups) Material: all solid wood Teaching aid The socket cylinder has four groups (A/B/C/D), which are similar in shape to the sleepers. There are (professional version of ten round holes), (family version of 5 round holes) and a cylinder with a small round handle. Suitable age More than 2.5 years old, you can use it when you enter the park. Direct purpose 1. Cultivate the ability of young children to visually identify the size and size, and let them learn how to do exercises. 2. Exercise the ability of young children to control movements with small muscles, hand-eye flexibility and coordination. 3. Develop their language skills and use vocabulary. Indirect purpose 1. Educate young children to find errors and correct mistakes. 2. Assist young children to concentrate and stimulate willingness to repeat operations. 3. Cultivate the child's concentration, order and observation.