Execution: Drive and connection parts according to DIN 3122 / 3123, external square according to DIN 3120 B 20 with spring-loaded pin, internal square according to DIN 3120 D 20 with hole and release button. Very stable construction, switchable for right and left rotation. Use: As a ratchet attachment for drive parts No. 645500 and 645605, but also as a ratchet for torque wrenches with a fixed 3/4 inch square drive.