1.Reliable bearing system 2.Fast drilling rate 3..size rang from3"1/2-26" 4.Certification: API & ISO9001 ... 5.delivery on time Type6"(152mm), 6 1/2 ... "(165mm), 8 1/2"(215.9mm), 9 1/2"(241.3mm), 12 1/4"(311mm) , 13 ... , 14 5/8"(371mm), 15"(381mm), 17 1/2"(445mm), 24"(609mm), 26"(660mm)IADC 147,437, ...