Supplied by OmniSwivel International, this 2nd stage cap seals the standard 9/16-inch fitting found on most regulator second stages. It protects the inlet threads and prevents contaminants from entering when the supply hose is disconnected. It is recommended for rebreathers to cover the external threads of the oxygen solenoid inlet port when not in use, for example when traveling. If you need the complete set including the cap and plug then see item OSI-DSS in the pricelist below.