Oxygen barrier crowns can be preferred over oxygen absorbing (or oxygen scavenging) caps for long term aging and storage of beer. The oxygen barrier liner does not let oxygen pass through, and has a special curved profile where the liner meets the top of the bottle. This prevents oxygen from intruding into the bottle. Oxygen absorbing crowns will absorb oxygen up to its saturation point, but after that oxygen can still enter the bottle throught the plastic liner. Oxygen absorbing crowns are recomended if the caps are used soon and manufacturing, and if the beer is consumed within 6 months.