Double row of teeth API 8 1/2" kingdream PDC bit 1-certified by API&ISO 2-A large stock 3-customered as your order ... bitMain TypeBit Diameters5 7/8",6",6 1/2",8 1/2",9 1/2",9 5/8",9 7/8",12 1 ... TypeMatrix or SteelBlades2~9 Wings.Cutter Sizes5/16"(8mm),1/2"(13mm),5/8"(16mm),3/4"(19mm),etc.Suitable Formation ... ,water well, mining, explorer well drilling. Double row of teeth API 8 1/2" kingdream PDC bit