This 1/2" ID (inner diameter) tubing is mainly used for racking and transferring. This size will fit perfectly on a large auto-siphon or racking cane. It is also perfect for making a blowoff assembly with a 3-piece airlock, as the tubing fits perfectly over the center of the airlock, allowing excess yeast and trub to be blown into a vessel filled with water or sanitizer. Always good to have on hand in a pinch.