Round burners are the best used when making round fire pits, fire features or fire pit tables. This is a mild steel burner so it should not be used outside or in damp settings because it will rust. But it is cheap so that is why people use them, what you should get is a stainless steel burner and we sell those too. These burners have a 1/2" female pipe connection. Note: the 12" and 18" have one ring the large burners have two burner rings to disperse flames more evenly.