The Oxygen Enrichment Connector Adapter's capped O2 port allows you to seal off the connector when not in use to keep your CPAP system running at full capacity without the hassle of removing the entire connector. The connector has a 22mm ID connection at one end and a 22mm OD connection at the other end to fit perfectly with standard CPAP tubing. This item is Latex free and made of sturdy plastic to resist breakage.