... by ISO and API, we have many regular customers in many countries and regions who are trading or drilling ... contractors. We have very good reputation in drilling field.Available sizes: 60mm,65mm,76mm,93mm,95mm ... 444.5mm(17 1/2”),508mm(20”),558mm(22”),609.6mm(24”)660.4mm(26”)Available models: Steel tooth(IADC)111, 121 ... ,522,532,612,622,632,7323 cone rotary rock bit 4 5/8"IADC537G