rubber and green fuzzies
In a usual match pack of balls there are 4 balls, but you can get tins with 2- 4 balls in them.
Yellow tennis balls are supposedly easier for the umpire to see if the ball was to land inside or outside of the boundary lines.
New tennis balls are considered fresh and not "flat". Old tennis balls exposed to play and air become flat and do not perform normally in a match.
The fuzziness of the ball gets grip from the surface and the felt rubs the surface of the court and thus causes friction. The denser the felt, the more friction and grip. The fuzz helps improve the...
rubber and air