Adult tennis racket head size midplus racket head size 645 cm head size inches 100 sq in stringing 16 x 19 levels professional advanced type of racket all round racket balance 320 mm recommended height from 155 cm weight unstrung 300 g racket balance head light grip size l0 l5 shape oval frame profile min 21 mm frame max 25 mm length 685 cm length inches 27 technology head graphene season 2015 series head effortless power