An aircraft landing gear shock absorber, the shock absorber comprising: a cylinder ; a piston assembly comprising a piston , the piston and piston assembly being mounted for movement relative to the cylinder; a stop surface arranged to limit extension of the shock absorber, wherein the stop surface is mounted on the cylinder and a load path extends between the stop surface and the cylinder via which the extension load on the stop surface is transferred, at least in part, to the cylinder; and a crumple element located on the load path and configured to plastically deform in the event that the extension load on the stop surface exceeds a predetermined threshold; wherein either: (a) the crumple element is a separate component and the properties of the crumple element differ from the properties of adjacent components and/or other components on the load path between the stop surface and the crumple element and/or between the stop surface and the cylinder such that the crumple element plastically deforms at a lower extension load than said other components; or (b) the crumple element is a region of a component and the properties of the crumple element differ from the properties of the rest of the component such that the crumple element plastically deforms at a lower extension load than the rest of the component. a cylinder ; a piston assembly comprising a piston , the piston and piston assembly being mounted for movement relative to the cylinder; a stop surface arranged to limit extension of the shock absorber, wherein the stop surface is mounted on the cylinder and a load path extends between the stop surface and the cylinder via which the extension load on the stop surface is transferred, at least in part, to the cylinder; and a crumple element located on the load path and configured to plastically deform in the event that the extension load on the stop surface exceeds a predetermined threshold; wherein either: (a) the crumple element is a separate component and the properties of the crumple element differ from the properties of adjacent components and/or other components on the load path between the stop surface and the crumple element and/or between the stop surface and the cylinder such that the crumple element plastically deforms at a lower extension load than said other components; or (b) the crumple element is a region of a component and the properties of the crumple element differ from the properties of the rest of the component such that the crumple element plastically deforms at a lower extension load than the rest of the component. (a) the crumple element is a separate component and the properties of the crumple element differ from the properties of adjacent components and/or other components on the load path between the stop surface and the crumple element and/or between the stop surface and the cylinder such that the crumple element plastically deforms at a lower extension load than said other components; or (b) the crumple element is a region of a component and the properties of the crumple element differ from the properties of the rest of the component such that the crumple element plastically deforms at a lower extension load than the rest of the component. <EOS>