A double-acting shock absorber (1) with progressive-damping stroke limiting device, particularly for vehicle suspensions comprising: a cylinder; a piston (6), which is constituted by a shaft (7) which slidingly and hermetically passes through the upper head of the cylinder, a plate being fixed to the lower end of the shaft (7), which is partly crossed axially by a hole (8a), the plate being able to slide hermetically in the cylinder; a pin (23) with a frustum-shaped tip (23a), which is fixed to the lower head (4) of the cylinder and is suitable to enter the hole (8a) of the shaft (7) in order to close it partially or completely. The shock absorber is constituted by a single plate (21) and comprises oil passage ports, which are provided in the plate (21) and in the shaft (7) and respectively connect one another the two faces of the plate, the face of the plate (21) that is directed toward the upper head to the hole (8a) of the shaft (7), and the lower inlet of the hole of the shaft to a region of the shaft that lies above the plate (21), two deformable membranes (31,32) being associated with the upper and lower surfaces of the plate (21) and being suitable to selectively block the ports fully or partially during the extension or compression of the shock absorber.
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