For use with tank systems that lack a second stage regulator such as drysuit inflation systems or rebreather cylinders. Both of these systems utilize a first stage regulator without need for a second stage and therefore need a fail-safe over pressurization valve if a high-pressure seat should fail. The First Stage Overpressure Relief Valve screws into any first stage low pressure port and is factory set to 180 psi. User adjustable with a max setting of 240psi.