There are many types of tire deflators on the market and there are several home made methods that work with varying degrees of effectiveness. Drilling tools are good, but if you're a clumsy guy like me, you can drop the core in deep sand or mud and never see it again. After a few minutes, when you throw in the sand/mud those spare cores you carry around because you know you're a clumsy too, you'll wish you'd never tried this method. Using the manometer takes a lot of time. If you're going to embark on this journey, you'll want to catch some air and get going. These deflators allow you to create pressure by adjusting the spring to hold the air valve open until the pressure of the exiting air can no longer be overcome by the spring and it snaps into place. In theory this works, but remember that you need to keep a close eye on them as they don't always close with a click but sometimes let air escape. However, this is the exception rather than the rule. For me the best way to use them is to put them all on and then see the first one install. As he approaches, touch the small part sticking out at the top. When he sits down, I walk around and shoot them all, making the necessary final adjustments with my meter. However, this is a small quirk. I'm very satisfied with this product. They are well made and I expect many years of service from them until I throw them in the deep mud and never see them again. (If I were lucky enough to find one, it would be very easy to disassemble, clean and reassemble the deflator.