The Dunlop FX 500 Tennis Racquet is built on the concept of controllable power. Dunlop's Sonic Core technology with Infinergy returns in the FX series. The elastic foam material produces a more dampened and comfortable response during contact. The "F" in FX refers to "Force" and it includes a few new game improvement innovations. The entire hoop incorporates a new Power Boost Groove under the grommets to elongate string movement and simultaneously create more power and comfort. The FX series features a new Aerodynamic Power head shape for improved mobility, and a wider throat section with improved stability. To make sure the power focused FX racquets remain comfortable, a unique high performance thermoplastic elastomer compound called Flex Touch Resin is built into the shaft. The material provides greater rebound off the string bed and improved vibration dampening when compared with a traditional graphite construction.