The ball must be white or orange, and matt, and must appear to be uniform and only have one seam.

Balls of the same brand must be identical in appearance, except that the same name may be used for white and orange balls.

The stamp on the ball must cover an area no greater than 280mm² and be printed in one or two colours, but the same stamp must be used for all balls of the same ball brand, product and colour.

In addition, the country of origin must appear on all balls.

All inscriptions must be easily readable and the trademark or brand name should be the most pronounced inscription, whilst the ITTF logo should stand alone.

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The official rules state that the ball shall weigh 2.7g, but any weight between 2.67 and 2.77g is acceptable for any one ball. No more than 1 ball out of the 24 sampled may be outside this range. The sample mean must be between 2.69 and 2.76g.

The official rules state that the ball shall have a diameter of 40mm.

This is measured using a calibrated electronic device with a precision of at least 0.001mm and the results are rounded to the nearest 0.01mm.

The minimum diameter of every ball must be at least 40.00mm and its maximum diameter must not exceed 40.55mm.

The sample mean average diameter, i.e. the mean of the average of the maximum and minimum diameters for each ball, must be in the range 40.00-40.40mm.

The official rules state that the ball shall be spherical.

The sphericity of a ball - or more correctly the lack of sphericity - is the absolute difference between its minimum and maximum diameters.

By rotating the ball about its axes, the minimum and maximum diameters are determined. The difference between the two values gives the lack of sphericity.

The sphericity of any ball must be less than 0.24mm, and the sample mean sphericity must be less than 0.17mm.

All balls must rebound to a height of not less than 240mm or more than 265mm when dropped from a height of 305mm on to a standard steel block.

All 24 balls must meet this test.

Veer is a measure of the total sphericity of the ball.

It's measured by rolling the ball down a slight incline onto a horizontal surface, and measuring the distance by which it deviates from a straight line as it rolls across the surface.

The incline is 100mm long at 14 degrees to the horizontal, and on a table that is 100cm long this gives a rolling time of about 3 seconds.

No more than two balls can deviate by more than 175mm from the center-line and each ball is measured at least three times.

Hardness is measured with a fully automated and computerised tester.

A 20mm diameter pin presses against a pole of the ball and the indentation is recorded to a precision of 0.01mm.

Measurements are made on each pole and the average for the poles provides a measure of the hardness.

Balls with a seam require a tolerance at poles between 0.68mm and 0.81mm.

Balls without a seam require a tolerance at poles between 0.70mm and 0.90mm.

The colour of the ball must meet the colour specifations which have been set for either white or orange, measured and calculated according to the CIE Lab system.

The measurements are performed on 3 points, one on the seam and two on other positions on the surface, of 4 balls randomly chosen from different boxes. If no seam is available three random points of measurement have to be taken.

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