Babolat Pure Drive Racquet with Cortex: The Babolat Pure Drive Racquet features Woofer technology, a patented innovation by Babolat which makes the frame and the strings interact when striking the ball. A tennis racquet is a frame with strings. The frame is basically static and holds the driving force of the racquet - the strings - in place. Woofer is the first technology which permits all of the strings to work together to their full potential when striking the ball, thanks to two functions: Piston function: enables larger uniformed string bed deformation on impact. Shock absorption: the pistons act like a suspension system to dampen vibrations Pully function: the strings act like a suspension system to dampen vibrations Woofer technology: Delivers 10% more power than conventional racquets, and ensures that the strings retain their energy longer Enlarges the sweetspot area for every racquet size Enables 25% more contact between the ball and the strings for optimal con