A flexible sleeve (212; 312) dimensioned for securement to an associated end member (206; 306) for an associated gas spring assembly (200; 300), said flexible sleeve (212; 312) comprising: a flexible wall (254; 354) having a longitudinal axis and extending circumferentially about said axis, said flexible wall (254; 354) including an inside surface (260; 360) adapted to at least partially define a spring chamber (214; 314), an outside surface (262; 362) opposite the inside surface (260; 360), an end surface (264; 364) disposed adjacent an open end (258; 358); an annular reinforcement member (268; 272; 372) being substantially fully embedded within said flexible wall (254; 354) adjacent said open end (258; 358); and at least one retainment element (274; 374) including an element surface, said at least one retainment element (274; 374) disposed along at least one of said inside surface (260; 360), said outside surface (262; 362) and said end surface (264; 364) of said flexible wall (254; 354) such that said element surface is at least partially exposed along said flexible wall (254; 354); wherein said at least one retainment element (274; 374) includes a first element surface and a second element surface opposite said first element surface, said at least one retainment element (274; 374) being at least partially embedded within said flexible wall (254; 354) such that said first element surface is in substantially full abutting engagement with said flexible wall (254; 354) and said second element surface is outwardly exposed along one of said inside surface (260; 360) and said outside surface (262; 362) of said flexible wall (254; 354); and wherein said at least one retainment element (274; 374) includes an inner element surface and an outer element surface disposed radially-outwardly of said inner element surface, said at least one retainment element (274; 374) being at least partially embedded within said flexible wall (254; 354) such that at least a portion of at least one of said inner element surface and said outer element surface is in abutting engagement with said flexible wall (254; 354) and a remaining portion of said at least one of said inner element surface and said outer element surface is outwardly exposed along at least one of said end surface (264; 364) and said one of said inside surface (260; 360) and said outside surface (262; 362) of said flexible wall (254; 354), wherein said at least one retainment element (274; 374) has the form of an annular ring which extends circumferentially about said longitudinal axis. a flexible wall (254; 354) having a longitudinal axis and extending circumferentially about said axis, said flexible wall (254; 354) including an inside surface (260; 360) adapted to at least partially define a spring chamber (214; 314), an outside surface (262; 362) opposite the inside surface (260; 360), an end surface (264; 364) disposed adjacent an open end (258; 358); an annular reinforcement member (268; 272; 372) being substantially fully embedded within said flexible wall (254; 354) adjacent said open end (258; 358); and at least one retainment element (274; 374) including an element surface, said at least one retainment element (274; 374) disposed along at least one of said inside surface (260; 360), said outside surface (262; 362) and said end surface (264; 364) of said flexible wall (254; 354) such that said element surface is at least partially exposed along said flexible wall (254; 354); wherein said at least one retainment element (274; 374) includes a first element surface and a second element surface opposite said first element surface, said at least one retainment element (274; 374) being at least partially embedded within said flexible wall (254; 354) such that said first element surface is in substantially full abutting engagement with said flexible wall (254; 354) and said second element surface is outwardly exposed along one of said inside surface (260; 360) and said outside surface (262; 362) of said flexible wall (254; 354); and wherein said at least one retainment element (274; 374) includes an inner element surface and an outer element surface disposed radially-outwardly of said inner element surface, said at least one retainment element (274; 374) being at least partially embedded within said flexible wall (254; 354) such that at least a portion of at least one of said inner element surface and said outer element surface is in abutting engagement with said flexible wall (254; 354) and a remaining portion of said at least one of said inner element surface and said outer element surface is outwardly exposed along at least one of said end surface (264; 364) and said one of said inside surface (260; 360) and said outside surface (262; 362) of said flexible wall (254; 354), wherein said at least one retainment element (274; 374) has the form of an annular ring which extends circumferentially about said longitudinal axis.