I bought this to test natural gas lines. It helped find a problem seeing how lines leaked over the course of minutes. Once I got to a good section of pipe I discovered this was a leak source of its own of about 0.004 lbs/min, which means 10min tests are fine but testing over the course of hours or days will require some improvements. I re-installed the pressure gauge with rector seal t 2 multi purpose white paste and seems to be good now since I can no longer hear the leak.

Update: I took off the air valve and redid the seal which was found to have a minor leak too. There are still minor leaks coming from this but not terribly bad. I would like to have a good seal for days since I'm doing a good amount of new gas piping, but short tests are still ok. I'd be curious if someone makes a better one for a tiny bit more but haven't found one yet, so review stays at 4 stars.

Worked fine. I did some DIY gas piping and I wanted to be 100 percent sure there were no leaks. (Note: this thing is assembled very tightly BUT there is no tape or pipe dope on it (duhhhhh!!) so you have to take apart, add pipe dope, and reassemble it, or it will leak like a sieve. Don't forget!!)

Easy to install. It is 3/4" female threade, I has a port as well, I believe it is 1/8".

Anything below 1PSI will be guess work, it will only start from 1/2 PSI, you may think it is not working if you get pressure under 1/2 PSI, which got me confused if the gadget was working, it was, the needle hardly move under 3/4 PSI, so don't send it back, it is the low pressure.

If you need accuracy under 1PSI you will be better off with a different model.

Good for the price, study enough, although I installed it permanently in a gas line after a shut off valve since I can't be sure if longer term use is reliable, I only turn it on when I want to check the pressure, when come to gas line if you do not need a gadget on 24/7, use after a shut off valve for safety.

For the price, I think it's a steal. I have bought around 20 and will continue to buy them. I use them for gas pressure testing. The ones I used to get always had a leak like 1-2 out of 10. Fail inspection is not my goal, cost me money, so far not one failure from not holding pressure.

The first valve read 4.5psi when not connected, so I sent it back and got another.
The second valve appears to work perfectly! Before I used it, I put pipe dope on the treads for the valve and gauge, based on other reviews. Then I connected it to a 3" nipple and a cap, and pressurized it to 15psi as a test. Very little total volume, so this is a very revealing test. After 24 hours, it is still exactly at 15psi, where it started.
Now I have confidence in the gauge, so if it shows a leak, I know I need to fix something.
If first valve had worked, I would have given 4 stars.