Junior tennis racket head size midplus racket head size 645 cm head size inches 100 sq in stringing 14 x 15 balance 290 mm recommended height 116 128 cm weight unstrung 210 g grip circumference 100 102 mm racket balance head light grip size l0 frame material graphite shape oval frame profile min 23 mm frame max 23 mm length 584 cm length inches 23 series prince tour