The Roto Grip Duo bowling ball utilizes a dynamically powerful core. This Mentor core was designed to generate midlane motion and produce a good measure of recovery at the backend. This upper-mid-performance ball uses the famous MicroTrax Pearl Reactive coverstock that stores energy through the front of the lane and unleashes that energy on the pins where it is needed. This ball not only has a dynamic look but also displays a dynamic motion on medium to medium/heavy oil conditions.