8 per cent cobolt for long life and endurance. Precision ground flutes, Faster drilling. Specially hardened for impact wrench use. 135 per cent split point angle for easy starting & accuracy. Goldmax titanium coating to stop heat burn-out. Set 3 Contains: 5.0, 6.0, 6.8, 8.0, 8.5, 10.0, 10.2mm. Set 4 Contains: 12, 13, 14, 16, 18, 20, 22mm.