Junior tennis racket head size midsize racket head size 516 cm head size inches 80 sq in stringing 16 x 15 balance 230 mm recommended height 92 104 cm weight unstrung 161 g racket balance head light frame material titanium shape oval frame profile min 19 mm frame max 19 mm length 482 cm length inches 19 player roger federer rec tension 19 kgs 2 kgs