Adult tennis racket head size midplus racket head size 645 cm head size inches 100 sq in stringing 16 x 19 string tension 22 26 kg level professional type of racket tournament racket playing properties control power balance 340 mm recommended height from 155 cm weight unstrung 265 g racket balance even grip size l0 l5 shape oval frame profile min 25 mm frame max 25 mm length 685 cm length inches 27 technology head graphene