... alloy steel and premium tungsten carbide insert, plus state of art welding technology and multiple precision heat treatment to ... 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 ... cn1000271447name: abdllahchina yang API 4 1/4"kingdream 3 blades of drag bit for soft formations