Adult tennis racket head size oversize racket head size 677 cm head size inches 105 sq in stringing 16 x 15 level beginner type of racket comfort racket playing properties spin balance 325 mm weight unstrung 305 g racket balance head light grip size l1 l4 frame material basalt shape oval frame profile min 26 mm frame max 26 mm length 699 cm length inches 28 technologies wilson spin effect technology wilson amplifeel 360 wils