Works great. You must install them before going outside. The day before I had inflated a tire to 12psi and loosened the top. I then put the deflator on the valve stem and tightened the top so no air could be heard. I tightened the lock nut on the top and removed it. I tested this twice on a different tire and it successfully dropped to 12psi. I then repeated the process with all 4 tire deflators and marked with a marker from top to bottom in case each was unscrewed or adjusted. I always check the tire pressures when I take them off and they are within psi of what I want. It really helps deflate 35 inch tires.