Adult tennis racket head size oversize racket head size 703 cm head size inches 109 sq in stringing 16 x 20 level beginner type of racket comfort racket balance 355 mm recommended height from 155 cm weight unstrung 255 g racket balance head heavy stiffness 70 ra grip size l0 l4 frame material graphite shape oval length 685 cm length inches 27 technologies babolat woofer system babolat intermediate cortex series babolat drive ad