Wera 05160901001 853/4 1/4'' Hex Harpoon Phillips ACR Power Drive Bits are high quality bits with reduced shaft diameter for low-lying screw connections allowing the countersinking of screws without any surface damage. Wera 853/4 1/4'' Hex Harpoon Phillips ACR ® Power Drive Bits feature rough ribs (anti cam-out feature, ACR) to prevent any slipping out of the screw head. Wera 853/4 1/4'' Hex Harpoon Phillips ACR ® Power Drive Bits are suitable for holders as per DIN ISO 1173-F 6.3.