This is the Zeagle Isolator Shut-off Valve for Second Stage Regulator Features: The Isolator Valve is used to shut off the air supply in any situation where 2nd stage isolation is desired. It attaches in line between the 2nd stage and the low pressure hose. Provides a shut off valve for a 2nd stage regulator. Excellent for an octopus regulator in swift current or any entry that could cause an octopus to free flow.