Wera 05059530001 851/4 BDC 1/4'' Hex Phillips Insert Bits are designed for phillips screws with tiny diamond particles on the bit tip. This ensures a secure fit of the bit in the screw, reduces the contact pressure required and lowers the risk of slipping. Wera 851/4 BDC 1/4'' Hex Phillips ® Power Drive Bits also feature BiTorsion technology where kinetic energy is diverted from peak loads and softer BiTorsion zone to prevent the bit tip from twisting under peak loads greatly extends the product service life. Wera 851/4 BDC 1/4'' Hex Phillips ® Power Drive Bits are suitable for holders as per DIN ISO 1173-F 6.3.