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.
WYNNsky Heavy Duty Dual Head Tire Inflator Gauge With 12 Inch Air Hose,Tire Pressure Gauge With Storage Case
32 Review
ποΈ Steelman Yellow Tire Marking Crayons: Identify Tire Damage with Ease, Box of 12
19 Review
Tonometer B.Well PRO-39
23 Review
Protein Prime Kraft Whey, 900 gr., tiramisu
25 Review
Xiaomi Mijia Ratchet Screwdriver 16 in 1 Screwdriver with Interchangeable Bits, 10 pcs, Black
22 Review
Reversible Mi 16-in-1 Ratchet Screwdriver
21 Review
DVR 70MAI Dash Cam Pro Plus+, black (A500S), black
87 Review
Bit and socket set Stels Tool set, 1/2", 1/4", CrV, plastic case 94 pcs, Stels, 94 pcs, black
46 Review