I have a portable gas grill and I usually do not leave the tank connected to the grill. I have a 5ft hose between the 20lb propane cylinder and the grill and when I disconnect the hose, the hose end is left exposed. I assume bugs, etc will nest in the open hose end and snow in the winter time. This fitting provides proper closure for the exposed end of the hose. The little black strap shown in the photo is mis-leading. You are led to believe you should pass the hose (in my case) through the loop to secure the cap, but that is not the case. The loop is very strechy and one of the ends, presently securred by the button on the top of the cap can be streched over the hose end so the cap is not lost when connected to the grill. The threads are will sized and easily allow the cap to thread on the end of the hose. Although I do not use the 1lb propane cylinders, I assume the cap would work fine to provide a protective closure in that case as well. This item is machined brass and well made, not some stamped piece of crap like you find on the end of garden hoses.