I'm trying to seal full CO2 pressure - maybe 60barg. I'm interested in the reciprocating O ring glands that you mention. They sound like the sort of O rings used in my old 16 barg Norgren pneumatic cylinder. They were made with very soft elastomer and appeared to have a lip to seal the pressure. This old cylinder had two seals, but I only need one, as the pressure is at one side of the ram only. I have no idea where to get such seals, nor what the best material of construction would be. Any help would be appreciated.