Wera 05057751001 20 Pc. BTZ Phillips Bit-Box are designed with an an elastic torsion zone where kinetic energy is diverted to when peak loads prevail and a softer BiTorsion zone to prevent the bit tip from twisting during peak loads: this significantly prolongs the product service life. Wera 05057751001 20 Pc. BTZ Phillips Bit-Box are designed with a 1/4'' hex and are suitable for holders as per DIN ISO 1173-D 6.3.