Deep sleep. Living sleep refers to the yo-yo of ceramic bearing behind metal bearing, and dead sleep refers to the drum ball or butterfly ball of nylon bearing. Magnetic wave yo-yo is a drum ball or butterfly ball with nylon bearing. Dead sleep without clutch, live sleep with clutch. Yo-yo with clutch is only suitable for players without basic knowledge. Players with some basic knowledge strongly recommend yo-yo with clutch. Yo-yo, a kind of spool, has a central axis connecting two bodies, most of which are axisymmetric, and moves back and forth by releasing rotating force and winding rope.