Working condition of the rock bit in directional and horizontal drilling applications is quite different than in vertical well drilling .our factory’s new MD series motor bit features high RPM , Better gage protection and stability ,higher reliability, excellent hydraulic effect and longer working life etc.MD bit is suitable for drilling at 90~300 RPM and is the ideal choice for directional ,horizontal and horizontal multilateral well drilling applications. The size range of MD series rock bit is from 7 7/8 to 12 1/4 inch ,and IADC varies from 117 to 647. for example:8 1/2MD517X.