The 1/2" inner diameter tubing is ideal for racking canes to get on and off of racking canes, spigots and bottle fillers, but not as airtight as the 11/16" tubing. To prevent air from getting into your racking tube use a clamp which will make it easily transferrable between your equipment and provide the proper seal.
Tip: If you heat the tubing in a glass of hot water before connecting it will make the whole connection easier on you.
This hose can be used to turn a 3 piece airlock into a blow off tube set up. But it is not as sturdy as the 11/16"