I buy at Home Depot/Lowes. Last time I bought clamps, I bought an even amount, so I could buy longer pipe (cheaper) and cut it in half myself. You only need one end threaded (after it's cut). I noted the last time I bought at HD, they said they don't cut and thread anymore, presumably due to liability (home owners doing their own gas work), which is completely stupid, since you can buy the pre-threaded pipe.