Wera 05059810001 851/4 TZ 1/4'' Hex Phillips Power Drive Bits are high quality bits for phillips screws that feature torsion zone for the absorption of peak loads which greatly extends the product service life. Wera 851/4 TZ 1/4'' Hex Phillips ® Power Drive Bits are ductile and tough for hard materials and feature Wera's Connecting Series 4. Wera 851/4 TZ 1/4'' Hex Phillips ® Power Drive Bit are suitable for holders as per DIN ISO 1173-F 6.3.