extra-duty

alternative extra duty

1. not comparablehobbiesDescribing a tennis ball having a thicker felt woven more loosely around the ball's core, designed for hard court surfaces such as asphalt or concrete.

   Coordinate term: regular-duty

   1 more example

   The men at the U.S. Open use what is known as an “extra-duty” ball, which means the felt on the outside of the ball is woven slightly more loosely than the “regular-duty” ball the women use. […] Extra-duty balls are the balls of choice for outdoor hardcourts, like those at the U.S. Open, except when they are not.

   2022 September 6, Matthew Futterman, “The Great U.S. Open Ball Debate of 2022”, in The New York Times