A 3/8 Male Flare to 3/8 Male Iron Pipe (MIP) Adapter (Union) can be used to extend a natural gas grill's hose with another natural gas hose that has a 3/8 female flare on one end and a quick connect/disconnect fitting on the other. A 3/8 iron pipe to quick connect/disconnect coupler is needed. (They come with our 10 foot natural gas hoses and all new Weber® natural gas grills.)You can also attach the 'natural' gas hose to the hose end of an LP tank's hose and regulator.(Note that 3/8 is the inside diameter (ID). The outside diameters (OD) are about 5/8.)Due to losses in the hoses and fittings, whenever you extend hoses you loose pressure and your grill/heater/roaster may not have enough gas to work properly. (Weber® grills should have 10 or 11 inches of water (water column) - a method of measuring the pressure.)This brass fitting needs plumber's putty or yellow gas pipe tape only on the pipe thread side to reduce the chance of leaking. Do NOT use putty or pipe tape on flare fittings. (The photo shows the flare fitting on the top and the pipe fitting side on the bottom. Photo is generic and doesn't accurately show the relative sizes of each end.)The adapter is also called a half-union.