A 15 Piece heavy-duty Impact Driver Set in a robust oil-resistant case. When used in conjunction with a medium-sized hammer, an impact driver will loosen or tighten stubborn screws and bolts. Contents :12 x Impact bits: 6 x 36 Flat, 8 x 36 Flat, 10 x 36 Flat, 12 x 36 Flat, PH1, PH2, PH3, PH4,4 mm Hex, 5 mm Hex, 6 mm Hex, 8 mm Hex 1 x 1/2in Drive heavy-duty reversible impact driver1 x 1/2in Drive impact coupler adaptor1 x Hex x 3/8in male adaptor.