... quality alloy steel and premium tungsten carbide insert, plus state of art welding technology and multiple precision heat treatment to provide ... formation and are used in areas that contain a lot of rock and also in the oil field. longer life and ... fast cutting,many size.Sizes: 3 3/4", 3.7/8", 4", 41/4", 55/8 ", 47/8", 6", 7.3/8 ... /8", 5.5/8", 5.7/8", 6.1/4", 6.3/4", 6.5/8" 7.3/8" 9.7/8 ...