For absorbing extreme peak loads when used in IMPACT screwdrivers. When used in combination with IMPAKTOR bits, the integral double torsion spring creates the first Tri-Torsion system in the world. It provides working lives up to 10 times longer than standard bits. Shank machine E 6.3 (1/4 inch), bit holder to DIN 3126 D 6.3 (1/4 inch).