APPENDIX K ITF RULES OF TENNIS b. The ball shall conform to one of the types specified in the table  immediately below or in the table under paragraph (d). Type 1  (Fast) Type 2  (Medium) 1 Type 3  (Slow) 2 High  Altitude 3 Weight (Mass) 56.0-59.4  grams (1.975-2.095  ounces) 56.0-59.4  grams (1.975-2.095  ounces) 56.0-59.4  grams (1.975-2.095  ounces) 56.0-59.4  grams (1.975-2.095  ounces) Size 6.54-6.86 cm (2.57-2.70  inches) 6.54-6.86 cm (2.57-2.70  inches) 7.00-7.30 cm (2.76-2.87  inches)  6.54-6.86 cm (2.57-2.70  inches) Rebound 138-151 cm (54-60 inches) 135-147 cm (53-58 inches) 135-147 cm (53-58 inches)  122-135 cm (48-53 inches) Forward  Deformation 4 0.56-0.74 cm (0.220-0.291  inches) 0.56-0.74 cm (0.220-0.291  inches) 0.56-0.74 cm (0.220-0.291  inches) 0.56-0.74 cm (0.220-0.291  inches) Return  Deformation 4 0.74-1.08 cm (0.291-0.425  inches) 0.80-1.08 cm (0.315-0.425  inches) 0.80-1.08 cm (0.315-0.425  inches) 0.80-1.08 cm (0.315-0.425  inches) Colour white or yellow white or yellow white or yellow white or yellow Notes: 1  This ball type may be pressurised or pressureless. The pressureless ball shall have an internal  pressure that is no greater than 7kPa (1 psi) and may be used for high altitude play above  1,219 m (4,000 feet) above sea level and shall have been acclimatised for 60 days or more at  the altitude of the specific tournament. 2  This ball type is also recommended for high altitude play on any court surface type above  1,219 m (4,000 feet) above sea level. 3  This ball type is pressurised and is specified for high altitude play above 1,219 m (4,000 feet)  above sea level only. 4  The deformation shall be the average of a single reading along each of three perpendicular  axes. No two individual readings shall differ by more than 0.08 cm (0.031 inches). c.  In addition, all ball types specified under paragraph (b) shall conform to  the requirements for durability as shown in the following table: MASS (WEIGHT) REBOUND FORWARD DEFORMATION RETURN DEFORMATION MAXIMUM  CHANGE 1 0.4 grams (0.014 ounces) 4.0 cm (1.6 inches) 0.08 cm (0.031 inches) 0.10 cm (0.039 inches) 462