Use is to connect the racking port valve, on the side of the conical, to a tube for filling a keg or bottle.
The adapter has 1/2 inch male thread on one end and is a 3/8 inch male barb connector on the opposite end. The tubing pushes over the bard end of the fitting and the male threads screw into the 1/2 inch ball valve.
The male threads will also fit the mash tun, hot liquor tank or any 1/2 inch female thread.