Product Overview The first introduction to the Pro Series, Specter 3 gets a massive overhaul. Our new RevFoam™ ATPU foam delivers serious energy return in a lighter package, while the redesigned rocker geometry offers a faster toe off. An ATPU insole cuts even more weight and provides additional rebound directly below the foot. We upped the already max-cushioned platform to keep you more comfortable and protected during hard efforts. The revamped outsole toughens up for increased traction and durability.