The Pressure Relief Valve (PRV) automatically releases any excess pressure built up inside a watertight enclosure. It works automatically, but it can also be opened manually or used to perform a vacuum test on your enclosure! We strongly recommend using the PRV on our locking watertight enclosures. SKU: BR-100804 HS Code: 7616.10.0000 Contents - 1 x Pressure Relief Valve Assembly (PRV Plug and Bulkhead) - 1 x M10 Nut - 1 x O-ring for Bulkhead