Adult tennis racket head size oversize racket head size 658 cm head size inches 102 sq in stringing 16 x 20 level professional type of racket all round racket playing properties control power balance 340 mm weight unstrung 249 g racket balance even stiffness 68 ra shape oval frame profile min 24 mm frame max 24 mm length 686 cm technologies wilson blx wilson double hole technology wilson parallel drilling season 2017 series wilso