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 spin balance 325 mm recommended height from 155 cm weight unstrung 290 g racket balance head light grip size l0 l4 frame material graphite shape oval length 686 cm length inches 27 technologies wilson amplifeel technology wilson spin effect technology seaso