Adult tennis racket head size oversize racket head size 677 cm head size inches 105 sq in stringing 16 x 19 level beginner type of racket comfort racket balance 350 mm recommended height from 155 cm weight unstrung 265 g racket balance head heavy stiffness 71 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