You know that the coverstock is critical to ball motion, so even when testing on a shorter oil pattern, even a milder version of Sure Grip II with the Photon core was too much. We decided to step it down a notch and go ‘Old School’ with the new Retrothane™ shell because predictable ball reaction never goes out of style! The Retrothane is a traditional urethane coverstock that will help you tame even the most scorching lane conditions. As witnessed on the PBA Tour and in World Championship events, urethane is still effective today. Redefine your arsenal with the new Grenade and know that no matter what they throw at you, Roto Grip has you covered. Roto Grip – we’re pulling the pin, tossing the Grenade and shaking it up.