The SPI LAB Series introduces the Concept, our next innovative release that reverses the narrative on how core/cover combinations are developed for challenging patterns. The ARC Cover has the highest coefficient of friction (COF) values and is right at the USBC limit on oil absorption time. With the Concept the coverstock acts as both the engine and the tires, while the Radius Weight Block behaves as the traction control - making sure the ball stays on-line to find the pocket. Since the coverstock is so strong and the weight block is very conservative in terms of RG/Diff, the Concept never wants to "lock up" or go forward down the lane. Even though the diff is very low, the cover technology ensures the ball does not carry oil down the lane as urethane is known to do. The cover forces the ball to continue hooking through the pins. The Concept, in the 14 - 16 pound weights, is a two-piece ball with a thick resin shell. The thicker shell raises the coefficient of restitution (COR) which has been shown tocreate more lively pin action.