The Counter Pressure Bottle Filler is a device that allows you to bottle beer after it has been chilled and carbonated in the keg. Without counter-pressure on the keg and bottle you would get a lot of foam, making bottling difficult.
Everything you need to make a counter pressure bottle filler. (Except the stoppers). I have a gallon growler, 22 oz bottle and a 12 oz bottle just to make sure I get the right length for copper tubing.