1). High quality and competitive price 2). many years experience in well drilling equipments Available sizes:4 5/8"(118mm), 5 7/8"(149mm), 6"(152mm), 6 1/2"(165mm), 6 5/8"(168mm),7 1/2"(190mm), 7 7/8"(200mm),8 1/2"(215.9mm), 9 1/2"(241mm),9 5/8"(245mm), 11 5/8"(295mm),12 1/4"(311mm), 13 5/8"(346mm),14 3/4"(374mm), 15 1/2"(394mm)16"(406mm), 17 1/2"(445mm),18"(457mm), 26"(660mm)Model NO.437,447,517 ...