... 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", 4.3/4",5.1/8", 5.5/8", 5.7/8", 6.1/4 ... ", 6.3/4", 6.5/8" 7.3/8" 9 ... not hesitate to contact ustrade manager: cn1000271447name: abdllahchina yang API 4 1/4"kingdream 3 blades of drag bit for soft formations