Highland S/S Tank Din Dust Cap We Buy these in bulk to save money you save 37% Please Note: This is the style without the groove this way you do not have to worry about your threads being destroyrd by the groove. The dust cap keeps crap out of your valve. This way when you put your regulator on there is nothing in there to keep it from sealing. Precision machined from 316L stainless steel Protects 200 and 300 bar DIN threads Seals water out with Viton o-ring for oxygen compatibility No groove through threads Stainless Steel This version not only keeps dust out of the valve but also seals tight to keep gas from leaking out. Divers buy this version off us more to keep the expensive gas from leaking if a handwheel is inadvertently bumped. An important thing to remember is if you do bump the handwheel and you have a cave fill you will play hell getting the plug out. This version also protects against smacking your valve or manifold.