Roller kelly bushing is a necesssary tool for drilling. It is to drive kelly spinner by matching with master bushing .Though rotating of four rollars ,the friction between rollars and kelly pipe is reduced and service life is extended. For different sizes of kelly pipe and hexagonal pipe only need to chang correct with rotary table , there are two drive styles(square and pin).The product is designed and manufactured according to API Spec 7K"Specification for Drill Equipment".