Table tennis balls are made from a lightweight plastic and are roughly 40 millimetres across.

The longer version

The shell is a hollow sphere of moulded polymer, thin enough that a fingernail can deform it and light enough to be slowed noticeably by air. At roughly 40 millimetres across it is larger than the size used before 2000, a change made deliberately to add drag and take speed out of the game. Seams left by moulding are polished away so flight stays true.

Because the mass is tiny, spin dominates: the ball can be struck so that it curves sharply or kicks forward off the table. Bounce height is regulated by dropping it from a set height onto a standard surface. The switch to polymer removed the fire risk of the older material and made manufacture more consistent, though players argued about the sound for years.

Where this entry sits

Facts here look at the rules, equipment and odd histories behind familiar sports and games, from balls and rackets to cards, boards and playing fields. Expect small details about scoring quirks, stadium design and the long story of the Olympic Games. The full list sits on the Sports and Games page, where every entry is listed in order.