Tire Pressure Monitoring Valve Caps Sensor Gauge - Advanced Detection System, 50 PSI Sensing Air Alert Indicator for Cars, Trailers, Bikes - Chrome-Plated, Pack of 4

These are great and work as advertised.

I bought a 40 lb. set and a 51 lb. set, they're identical. You activate any of them by inflating your tires to the desired pressure clean the tire stem threads before installing (prevents leaks) then screw them on moderately tight. The trick is that they set themselves to the pressure in your tire the first time they sense pressure: That's what they maintain. I can find no other explanation as to how they work. I can also not find any way to talk to the manufacturer--period. Warning: Don't try one out with a tire on your car/truck UNTIL you've inflated to the proper pressure! If you do that stem will be set for that pressure. If I hadn't bought two sets for different pressures and found ZERO instructions on how to set the pressure and ZERO indication of the pressure they are for I'm sure I would have tried one to see how it looked and had one tire that showed green till the wrong pressure. Now all it takes a walk around and a trip to a local tire store for a free refill. Remember you gain 0.3 mpg for every extra lb of air. Including the extra air it's safe to run that's written on the sidewall of your tire that's set lower in your owners manual. There's serious savings to be had here.

Great quality. Have had over a year now and very satisfied. I would buy again. With that said they are pricey. But these are a real step up from the China junk out there.

I use these on my truck, car, boat and utility trailers. Available in a range of pressure settings for many applications. I run all my vehicle tires at maximum air pressure so they last longer and I get better fuel economy. A quick look tells me whether or not I need to add air. These work well and are fairly priced.

This set of 50# caps were junk... Caused a flat on the camper, within a week. Had tire check, confirmed valve cap issue. Sent a replacement set, that just pulled the same stunt

I've had these devices for 3 months and they have worked well....until this morning. My front tire was completely flat so I aired it up and drove to the tire store. After checking my tire extensively, they couldn't diagnose any issues. As they were putting the cap back on, the technician waved me over. The cap was completely tightened down but I could still hear a slight hissing noise of air escaping. So, 3 out of 4 of these worked as they should. However, the one that did fail was more than a little inconvenient, to say the least!

I have used these on my RV trailer for nine months and they work great. They are not as good as a electronic tire pressure monitor but they give you a quick look at the tires when stopping to rest or while getting gas fill up.

These are invaluable for use with my travel trailer. Checking the tire pressure using a pressure gauge is difficult due to the position of the valves. These let me see quickly if I'm ready to roll.

Do not work at all

these are well made and are pretty good, all you need is a quick look and if there green you're ok. tested with my rv tire they do the job well.

Pros: Easy to install & highly visible. Cons: Stuck out further than I thought.

Very easy to verify cold pressure on my trailer tires. Excellent product. I no longer have to check with a pressure gauge.

They worked as advertised. What else can I say?