Bought a mk 25 s600 the other day can someone answer my question? This is my question the first stage has 2 hp ports on the first stage it has what looks like a adapter it is about 1/2 long and has a plug in the end. Is it a adapter for a different size hose or is it a stand off for a a/i transmitter.Or what? It is on the side of your left ear if the reg was on a tank. Thanks