A sealing sleeve (1) for hydraulic installations is intended to seal a piston (4) movable axially parallel in a hydraulic cylinder (8) and has a peripheral sealing lip (5) having a sealing surface (9) to bear on a cylinder bore (7). According to the invention, the sealing surface (9) has a convex shape ending in a peripheral edge (10). This shape makes it possible for a variable fraction of the sealing surface (9) to bear on the cylinder bore (7) from a large-area to a linear bearing. An improved sealing effect is obtained, especially in extreme conditions, in a wheel cylinder (8) of a drum brake secured to a vehicle wheel during severe shaking and vibration, without the need for any compromises regarding the easy moving or pressureless actuation of the piston (4).
