Adult tennis racket head size midsize racket head size 619 cm head size inches 96 sq in stringing 16 x 20 level professional type of racket tournament racket playing properties spin balance 340 mm recommended height from 155 cm weight unstrung 305 g racket balance even grip size l1 l4 frame material basalt shape oval frame profile min 22 mm frame max 22 mm length 692 cm length inches 27 technologies wilson spin effect techn