Adapters - Fittings

For quick reference about the low-pressure breathing gas fittings^† seen on modern SCUBA regulators and hoses:

• First stage bodies have standard low-pressure outlet ports with UNF 3/8"-24 Female threads
• Some first stage bodies also have one non-standard outlet port with UNF 1/2"-20 Female threads and require a non-standard hose or an adapter
• LP hose standard inlets have UNF 3/8"-24 Male threads to mate with standard first stage low pressure ports
• LP hose standard outlets have UNF 9/16"-18 Female threads to mate with a standard second stage inlet
• Second stage bodies have a standard low-pressure inlet with UNF 9/16"-18 Male threads
• Some second stage bodies have a non-standard low-pressure inlets:
• Commercial diving full face masks may have M16x1 (aka AGA) inlets and require a non-standard hose or an adapter
• Pre-2008 Poseidon brand 2nd stages have inlet fittings unique to their design and require a non-standard hose or an adapter

† Low pressure Schrader QD fittings typically seen on BC power inflators can not be used for breathing gas applications due to an inherent flow restriction.

† High pressure fittings are UNF 7/16"-20 threads. Low pressure fittings should NEVER be adapted for use in high pressure applications.