ITF Tennis - Technical

	Overview
	Rules for equipment
		The Court
		Permanent Fixtures
		The Ball
		The Racket
		Appendix I
		Appendix II
		Plan of the Court
		Court Markings
	History of the rules
		The Ball
		The Racket
	Product conformity

Appendix I - The Ball

Ball in Ring Gauge

a. The ball shall have a uniform outer surface consisting of a fabric cover and shall be white or yellow in colour. If there are any seams they shall be stitchless.

b. More than one type of ball is specified. The ball shall conform to the requirements shown in the table below.

	TYPE 1 (FAST)	TYPE 2 (MEDIUM)¹	TYPE 3 (SLOW)²	HIGH ALTITUDE³
WEIGHT (MASS)	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 (56.0-59.4 grams)
SIZE	2.575-2.700 inches (6.541-6.858 cm)	2.575-2.700 inches (6.541-6.858 cm)	2.750-2.875 inches (6.985-7.303 cm)	2.575-2.700 inches (6.541-6.858 cm)
REBOUND	53-58 inches (135-147 cm)	53-58 inches (135-147 cm)	53-58 inches (135-147 cm)	48-53 inches (122-135 cm)
FORWARD DEFORMATION⁴	0.195-0.235 inches (0.495-0.597 cm)	0.220-0.290 inches (0.559-0.737 cm)	0.220-0.290 inches (0.559-0.737 cm)	0.220-0.290 inches (0.559-0.737 cm)
RETURN DEFORMATION⁴	0.265-0.360 inches (0.673-0.914 cm)	0.315-0.425 inches (0.800-1.080 cm)	0.315-0.425 inches (0.800-1.080 cm)	0.315-0.425 inches (0.800-1.080 cm)

Notes:

¹ This ball may be pressurised or pressureless. The pressureless ball shall have an internal pressure that is no greater than 1 psi (7 kPa) and may be used for high altitude play above 4,000 feet (1,219 m) above sea level and shall have been acclimatised for 60 days or more at the altitude of the specific tournament.

² This ball is also recommended for high altitude play on any court surface type above 4,000 feet (1,219 m) above sea level.

³ This ball is pressurised and is an additional ball specified for high altitude play above 4,000 feet (1,219 m) 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 .030 inches (.076 cm).

c. All tests for rebound, size and deformation shall be made in accordance with the
regulations below.

REGULATIONS FOR MAKING TESTS

i. Unless otherwise specified all tests shall be made at a temperature of approximately 68º Fahrenheit (20º Celsius), a relative humidity of approximately 60% and, unless otherwise specified, an atmospheric pressure of approximately 30 inches Hg (102 kPa). All balls shall be removed from their container and kept at the recognised temperature and humidity for 24 hours prior to testing, and shall be at that temperature and humidity when the test is commenced.

ii. Other standards may be fixed for localities where the average temperature, humidity or average barometric pressure at which the game is being played differ materially from 68º Fahrenheit (20º Celsius), 60% relative humidity and 30 inches Hg (102 kPa) respectively. Applications for such adjusted standards may be made by any National Association to the International Tennis Federation and, if approved, shall be adopted for such localities.

iii. In all tests for diameter, a ring gauge shall be used consisting of a metal plate, preferably non-corrosive, of a uniform thickness of one-eighth of an inch (0.318 cm). In the case of Ball Type 1 (fast speed) and Ball Type 2 (medium speed) balls there shall be two circular openings in the plate measuring 2.575 inches (6.541 cm) and 2.700 inches (6.858 cm) in diameter respectively. In the case of Ball Type 3 (slow speed) balls there shall be two circular openings in the plate measuring 2.750 inches (6.985 cm) and 2.875 inches (7.303 cm) in diameter respectively. The inner surface of the gauge shall have a convex profile with a radius of one-sixteenth of an inch (0.159 cm). The ball shall not drop through the smaller opening by its own weight in any orientation and shall drop through the larger opening by its own weight in all orientations.

iv. In all tests for deformation conducted under Rule 3, the machine designed by Percy Herbert Stevens and patented in Great Britain under Patent No. 230250, together with the subsequent additions and improvements thereto, including the modifications required to take return deformations, shall be employed. Other machines may be specified which give equivalent readings to the Stevens machine and these may be used for testing ball deformation where such machines have been given approval by the International Tennis Federation.

v. The procedure for carrying out tests is as follows and should take place in the order specified:

a. Pre-compression – before any ball is tested it shall be steadily compressed by approximately one inch (2.54 cm) on each of three diameters at right angles to one another in succession; this process to be carried out three times (nine compressions in all). All tests are to be completed within two hours of pre-compression.

b. Weight (mass) test.

c. Size test (as in paragraph iii. above).

d. Deformation test – the ball is placed in position on the modified Stevens machine so that neither platen of the machine is in contact with the cover seam. The contact weight is applied, the pointer and the mark brought level, and the dials set to zero. The test weight is placed on the beam in a position that is equivalent to a load of 18 lb (8.2 kg) on the ball, after which the wheel is turned at a uniform speed such that five seconds elapse from the instant the beam leaves its seat until the pointer is brought level with the mark. When turning ceases the reading is recorded (forward deformation). The wheel is turned again until figure ten is reached on the scale (one inch {2.54 cm} deformation). The wheel is then rotated in the opposite direction at a uniform speed (thus releasing pressure) until the beam pointer again coincides with the mark. After waiting ten seconds, the pointer is adjusted to the mark if necessary. The reading is then recorded (return deformation). This procedure is repeated on each ball across the two diameters at right angles to the initial position and to each other.

e. Rebound test (as above) – the ball is dropped from 100 inches (254 cm) onto a smooth rigid and horizontal surface. Measurements of both drop height and rebound height are to be taken from the surface to the bottom of the ball.

CLASSIFICATION OF COURT SURFACE PACE

The ITF test method used for determining the pace of a court surface is test method ITF CS 01/01 (ITF Surface Pace Rating) as described in the ITF publication entitled “An initial ITF study on performance standards for tennis court surfaces”.

Court surfaces which are found to have an ITF Surface Pace Rating of between 0 and 35 shall be classified as being Category 1 (slow pace). Examples of court surface types which conform to this classification will include most clay courts and other types of unbound mineral surface.

Court surfaces which are found to have an ITF Surface Pace Rating of between 30 and 45 shall be classified as being Category 2 (medium/medium-fast pace). Examples of court surface types which conform to this classification will include most hardcourts with various acrylic type coatings plus some textile surfaces.

Court surfaces which are found to have an ITF Surface Pace Rating of over 40 shall be classified as being Category 3 (fast pace). Examples of court surface types which conform to this classification will include most natural grass, artificial turf and some textile surfaces.

Note: The proposed overlap in ITF Surface Pace Rating values for the above categories is to allow some latitude in ball selection.

Case 1: Which ball type should be used on which court surface?

Decision: 3 different types of balls are approved for play under the Rules of Tennis, however:
a. Ball Type 1 (fast speed) is intended for play on slow pace court surfaces
b. Ball Type 2 (medium speed) is intended for play on medium/medium-fast pace court surfaces
c. Ball Type 3 (slow speed) is intended for play on fast pace court surfaces

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