Adult tennis racket head size oversize racket head size 658 cm head size inches 102 sq in stringing 16 x 19 level beginner type of racket comfort racket balance 340 mm recommended height from 155 cm weight unstrung 270 g racket balance even grip size l0 l5 shape oval frame profile min 21 mm frame max 26 mm length 685 cm length inches 27 technology head graphene season 2015 series head effortless power additional informati