Can be used with or without a spring, which makes it both a gravity filler and a spring bottle filler. Guaranteed not to leak. The main body can be unassembled from the acrylic tube for cleaning and is long enough to fit most bottles. Insert into bottle and push the filler down into the bottom. Remove the filler when the beer/wine reaches the top of the bottle for the perfect amount of head space. Use with 3/8" ID bottling hose.