A piston for a hydrostatic piston machine, especially an axial-piston pump or motor in which the piston is formed with a ball head riding in a slide shoe which is supported by a fluid-pressure cushion against a countersurface, e.g. a swashplate. The piston is formed with a central passage which communicates with a bore in the ball head, this bore being provided with a throttle to prevent the fluid medium from being forced at an excessive rate into the fluid-pressure cushion and thereby lift the shoe from the countersurface. According to the invention, the end of the piston remote from the ball head is provided with a gap filter of large area and narrow gap width to prevent large particles from entering and blocking the passage and the throttle.