MKP Master Bushings are designed for Square drive and Pin drive Kelly Bushings from sizes 17-1/2″ to 37-1/2″ rotary tables. The pin drive allows the use of extended insert bowls to meet flush with the top of the table which means better slip support and prevents damage to the drill pipe. The Square Drive Master Bushing has a 4″ deep recess to be used with the Square Drive Kelly Bushings. Short and medium style slips are used in the Square Drive for shallower depth and drilling.