Counter pressure Bottle Filler features a special valve on top that allows CO2 or beer to flow down the same stainless tube, directly to the bottom of the bottle. The valve has three positions, off, beer and CO2. The unit is inserted into the bottle in the off position. The valve is then turned to CO2 to flush the bottle and then to beer for filling. The adjustable pressure relief on the side of the unit allows you control the speed of fill by adjusting the pressure in the bottle. The valve is positioned in such a way that it is easy to use with one hand, while the other holds the bottle. This model is designed for 12oz bottles but can easily be extended to accommodate larger bottles, such as 22oz, with a small piece of 1/4″ tubing.