• High-performance alloy steel • Square female size: 1-1/2", 2-1/2" • Square male size: 1", 2-1/2", 1-1/2" • Phosphate finish • For maximum safety use clamping springs • With through-hole • D2 = outside diameter of the female end • Warning: torque applied should be limited to the smallest drive • Drive standard: DIN 3121, ISO 1174 • Standards: DIN 3129, ISO 2725