APPENDIX K ITF RULES OF TENNIS Note: In addition to the ball types specified under paragraph (b) above, the Stage 1  (Green) ball may be used for all levels of competitive play except for world ranking  professional tennis events, Davis Cup and Billie Jean King Cup, the Olympic  and Paralympic Tennis Events, World Tennis Tour Men’s, Women’s and Junior  Tournaments and Team events sanctioned by the ITF and affiliated Regional  Associations, ITF Senior Circuit and Team events and ITF Wheelchair Tennis Tour  Circuit and Team events. Each National Association shall have the right to decide which national competitive  events should use the Stage 1 (Green) ball. For all measurements in Appendix II, SI units shall take precedence APPENDIX II THE RACKET a.  The racket shall consist of a frame and string(s). The frame shall consist  of a handle and head, and may also include a throat. The head is defined  as that part of the racket to which the string(s) connect. The handle is  defined as that part of the racket connected to the head which is held  by the player in normal use. The throat, where present, is that part of the  racket that joins the handle to the head.  b. The hitting surface, defined as the main area of the stringing pattern  bordered by the points of entry of the strings into the head or points of  contact of the strings with the head, whichever is the smaller, shall be  flat and consist of a pattern of crossed strings, which shall be alternately  interlaced or bonded where they cross. The stringing pattern must be  generally uniform and, in particular, not less dense in the centre than in  any other area.  c.  The racket shall not exceed 73.7 cm (29.0 inches) in overall length, and  31.7 cm (12.5 inches) in overall width. The hitting surface shall not exceed  39.4 cm (15.5 inches) in overall length, when measured parallel to the  longitudinal axis of the handle, and 29.2 cm (11.5 inches) in overall width,  when measured perpendicular to the longitudinal axis of the handle. d. The racket shall be free of any attached object, protrusion or device  which makes it possible to change materially the shape of the racket, or  its moment of inertia about any principal axis, or to change any physical  property which may affect the performance of the racket during the  playing of a point. Attached objects, protrusions and devices that are  The racket shall be designed and strung such that the playing  characteristics are identical on both faces. 464