A ball (1) for valves is described, comprising a substantially ball-shaped body (2), a hole (4, 5) bored in the body (2) for fluid flow passage between the entry and exit of the valve, and a slot (10) cut into the body (2) to house a pin for ball (1) rotation. The ball (1) is produced in a single element, and the hole (4, 5) terminates in a wall (6) in which a specifically shaped opening (12) is cut to regulate the amount of fluid flow between the entry and exit of the valve.