Junior tennis racket head size midplus racket head size 632 cm head size inches 98 sq in stringing 16 x 20 balance 330 mm recommended height from 155 cm weight unstrung 280 g racket balance even grip size l2 l4 frame material graphite shape oval frame profile min 20 mm frame max 23 mm length 685 cm length inches 27 technologies yonex isometric yonex ips yonex 3d vector shaft yonex ops yonex super cushion grip series yon