This is a Venting On / Off adapter that you would attach to your ESG style grip frame or on your tank itself. This will allow you to simply turn off the outgoing air. This will let you unscrew your tank from your ESG grip or to stop the air going into your on tank regulator. A MUST part for all HPA user's. No more messing up your regulators threads! We have 2 styles and we do custom anodize these from time to time for sale on the site.