The Srixon PRO UR utilizes a solid rubber boundary layer which feels softer and has more resilience than a traditional ionomer (plastic) boundary layer found in competitive urethane golf balls. Poly-Amide added to the urethane material in the cover of the the Pro UR increases the resilience of the urethane cover. 432 dimple pattern utilizes 4 different size dimples for tremendous aerodynamic stability, lift and carry.