The MOTIV SR2 is engineered to destroy pins. The Sigma core produces a low RG for easy revs and a high differential for serious track flare. Combine this with MOTIVat-R reactive urethane on the cover and you have a deadly weapon of destruction in the palm your hand. Sigma Inner Core The Sigma core is the mechanism of destruction at the heart of the SR2. It provides a low RG for easy revs and a high differential for powerful track flare. The 15# SR2 has an RG of 2.47 and a .047 diff. MOTIVat-R Reactive Urethane The MOTIVat-R shell on the SR2 has never been combined with the Sigma core before. This cover provides a smooth, but very strong backend reaction. The SR2 is sanded to 2000 at the factory and then brought to a luster with Power Gel Polish. Reverb Outer Core The Reverb outer core of the SR2 is a low-density polyester resin with pin piercing hardness and strength. Rather than absorb impact energy, this outer core reverberates energy as it explodes through the pins. NeoMark Reactive Urethane Graphics The SR2 jet black coverstock is integrated with orange and white NeoMark logo graphics. These graphics are also formulated from MOTIVat-R reactive urethane so you have a consistent reaction 360° around the ball surface.