If you look on your 20# LP tank you may notice that it has threads on the outside where newer hose & regulators screw on by hand in a clockwise direction (righty-tighty, lefty-loosey). This the QCC1 connection. (QCC is quick closing coupler which in the US is 1 5/16-inch ACME threaded. See the large diameter threads on the right side of the adapter in the photo.)If you look closely, you'll see that there are threads on the inside of that QCC1 connection. Those threads are for the P.O.L. (or POL) connection. POL is reverse threaded meaning you tightens by screwing in the opposite direction. (See the red colored threads on the left of the adapter in the photo.) You use a wrench to tighten a POL connector.In the past, LP tanks used to all be attached to your grill (or my dad's travel trailer, back in the '60s) with a POL fitting.If you happen to come across some old tanks that have only the POL connection this QCC1/POL adapter will allow you to use your QCC1 hose & regulator to empty the tank. (The tank is likely past certification so you won't be able to get it refilled.)You might also use the QCC1/POL adapter in conjunction with a quick-connect fill plug to empty a quick-connect/disconnect tank with a QCC1/ACME grill's hose and regulator.815247 is OMC #11051 (but we may get them from somewhere else).There isn't much call for these so we may have to special order them in if we're out but they should ship the week after you order them or early the next week.