Colorful groove screwdriver bits 1.S2 steel 2.Different size for your chose 3.58-61 degree hardness 4.bits with two grooves 1.H1/4" 25mmL bits \ colorful groove screwdriver bits (screwdriver bits, power bits, pneumatic power bits)2.Application: screwdriver bits, power bits, pneumatic power bitsS2 material3.Wide range of Tips selection:1)Phillips,Slotted,Torx,Pozidriv,Quadrex,Frearson,Sockethead, ...