a hydraulic shock absorber including inner and outer tubes telescopically fitted together and an orifice variable in response to relative movement of the inner and outer tubes . a large diameter tubular holder is disposed coaxially around an upper portion of the outer tube to provide a space between the outer tube and the holder , the space being divided by a tubular partition membrane disposed coaxially in the space into a high - pressure gas chamber located outside of the membrane and a low - pressure gas chamber located inside of the membrane and communicating with an upper space within the outer tube . the shock absorber is of the hydraulically and pneumatically operated type , is simple in structure , and can be assembled with ease while maintaining a desired degree of performance . when the shock absorber is at the end of the extension stroke , there is a sufficient length of span between an outer tube sliding portion and an inner tube sliding portion between which the variable orifice is located so that even when the shock absorber is subjected to lateral bending forces , the orifice clearance is prevented from being varied or deformed , to ensure reliable and smooth operation of the shock absorber .