Adult tennis racket head size midplus racket head size 632 cm head size inches 98 sq in stringing 16 x 19 level professional type of racket tournament racket balance 310 mm recommended height from 155 cm weight unstrung 310 g racket balance head light grip size l1 l5 frame material graphite shape oval length 686 cm length inches 27 technologies yonex new isometric yonex aero shape yonex trans weight system yonex new ops yonex sho