Review on 🚗 AutoEC Adjustable Brass Tire Deflator Kit for Off Road Vehicles - Ideal for Car, Truck, Jeep, and ATV (Pack of 4) by Hector Mak

It seems to work fine. I manually powered them several times before making my first attempt at calibrating them. When you have the tire set to the desired pressure, turn it 1/8 after the hiss is closed. They seem to be more accurate above 15 pounds than below. Under 15lbs you have to watch out for the hiss - it starts out loud, then fades a bit and then becomes barely audible - once it's barely audible remove the deflator and check the pressure, you're probably where you need to be . They're not perfect, but they're not $90 either.