The wera 7 piece bi torsion diamond coated bit check set contains 7 pz ph sl bi torsion diamond bits bdc significantly extend service life and prevent cam out microscopic diamond particles literally bite into screwheads preventing slips the two unique torsion zones one in the bit and one in the holder work together to absorb peak loads placed on the bit extending bit service life diamond bits are also hardened to a higher degree than standard bits extending life further unique rapidaptor bit hol