... spiral flute, size: 4.0-12, 6.0-402) HSS step drills bits with spiral flute TiALN coating, size: 4.0 ... -12, 6.0-403) HSS step drills bits with spiral flute, Hex Shanks, size: 4.0 ... -12, 6.0-404) HSS step drills bits with spiral flute, Hex Shanks,3pcs! size: 4 ...