A pressure medium unit, in particular for setting and/or regulating a brake pressure in a vehicle brake system having electronic slip regulation, and to a cap-shaped filter element. Pressure medium units are equipped with a housing block having a duct formed therein that conducts pressure medium, a control element that controls a cross-section of the duct, and a filter element assigned to the control element and fixed in the interior of the duct. According to the present system, the filter element is formed in the shape of a cap, and has on its outer circumference a radially protruding fixing segment having an elastically deformable cross-section. A fixing segment realized in this manner compensates differences in expansion between the components caused by changes in temperature, prevents play at the filter element, and provides a particularly good filter effect.