koken - special heat treatment is applied on the bodyhardness of striking part is slightly softer to prevent crackson the other hand, cam part converts the striking power to twisted by striking with a hammer, therefore this part is finished with higher hardness to improve anti-wearstronger spring is adapted to convert the striking power efficiently to twisting power100p-32 phillips bits - #2, #3100s-32 flat bits 9, 11mm4112n - 1/2" dr attack driver4138 - 1/2" dr bit holder