This sample valve most definitely does not come with a 1/2" barb and definitely does not accommodate 1/2" tubing. The barb is much smaller.

Bought this to use as a bleed valve on the outlet side of my pump and the barb is for 1/2" tubing. Maybe they have changed the design since the previous review.

I use these on top of both of my March pumps with a tee. These valves are excellent for bleeding the air out of the pumps. Just open the valve until water or wort comes out and the air is successfully purged from the pumps and they will prime every time! Also great for taking a sample for gravity readings. A short piece of 1/2 inch tubing will slide over the barbs on mine with ease and do not need a clamp and do not leak if your just taking a small sample. If you need to have tubing more permanently attached to your valves, or are using them to draw off a large amount of liquid, then you will need clamps, as the barbs are smaller than 1/2 inch on mine. Quality product!