I got a metal one with a gauge so that I could see what pressure I had in the hose. The regulator attaches to the faucet. Next, the gauge tells me the line pressure I am delivering to the hose and the plumbing of the trailer.
I've had this for three years now and it has not failed. But if the gauge DOES fail, it's a separate device that is easily replaced. I wanted to make sure the regulator was doing it's job.
And, neither one is expensive.
Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew