The deepened drive end of the KO-KEN Sleeve-Drive tools prevents the sometimes "wobbly" connection between pulse tool - extension - socket. An O-ring inside Sleeve-Drive optimizes the perfect fit of extension bars and sockets on the anvil to the effect, that the exactness of the required torque given by the pulse tool Sleeve Drive Extension Bar 3/8" Sq.Dr. 125mm with Pin (ACK Type)