API 7K Casing Bushing Insert Bowls for Oil Drilling Rig This bushing is an essential tool for petroleum drilling. It mates with the rotary table master bushing to drive the kelly. Fitted with four rollers, it reduces friction against the kelly during rotation and extends service life of the kelly. For square and hexagon kellys of different sizes, matching can be achieved by replacing the rollers. It is compatible with various types of rotary tables and is available in two