Adult tennis racket head size midsize racket head size 626 cm head size inches 97 sq in stringing 18 x 16 level professional type of racket tournament racket playing properties power spin balance 325 mm weight unstrung 270 g racket balance head light grip size l0 l3 frame material graphite shape oval length 685 cm technology wilson spin effect technology season 2016 special feature compatible with smart tennis sensor colour grey ad