Nothin special... 50 ft of 3/8 od copper, $40 at lowes. Odd combo of essentially useless fittings and a ball valve. Don't need em, but I had em, so why not use em! Coiled top to bottom, then back up the middle with one coil stretched the whole length to the top and soldered to every outside coil. Overkill? Probably. Perfect? No. But cost me a hell of a lot less than buying one!