I don't usually write reviews but I wouldn't recommend them for large tires. I run 37" tires and bought these to replace the Oasis Trailhead deflators I have used for years. The gauge deflator works great for the price if you are young and have good knees. The copper protection on the deflators sticks strongly and very slowly. I tested speed and accuracy and didn't have the patience to wait for either of them to deflate from 20psi to 15psi. In 5 minutes he dumped just a few pounds per square inch. It looks like the vent holes are so small that it would take a very long time to get my 37" tires from the 35psi to the 15psi I was aiming for. They can work well for smaller tires if you have the patience and budget.