Tough/hard. For universal use. With torsion zone. For use with hand and power tools (conventional cordless screwdriver)Drive for 25 mm length: 6.3 mm (1/4″) hexagon in accordance with DIN ISO 1173 C 6.3Drive for 50 mm length: 6.3 mm (1/4″) hexagon in accordance with DIN ISO 1173 E 6.3