Real tennis balls are handmade by club professionals. Each ball contains a core wrapped around with some thirteen yards of webbing in half-inch widths. The webbing having been wetted is tightly wound like wool into a ball and is then moulded on a special bench into a spherical shape. When moulded, the ball is then tied with twine, again on an attachment fitted to the special bench, the process being repeated three times before a ball tightly bound with only triangles of webbing showing through the binding is ready for covering. The covering, which is sourced from one factory in the UK, is made of wool cloth which is hand sewn on to the core with thin thread. In view of the heavy use to which most balls are put, each ball will have to be re-covered about once a fortnight. The core, however, only wears out after many years.
It used to be said that the uniform of French prisoners-of-war imprisoned in England during the Napoleonic wars 1799-1815 was used with great success in making the balls for the royal tennis court. The method of making balls is largely unchanged for the last few hundred years.
Compared to lawn tennis balls, real tennis balls are relatively hard, and bounce fast and low.