They call it a booster pump but it can't. First you can only let it run 14 minutes, then you have to let it ""cool down" for 35 minutes. Here's what you get in those 14 minutes (from scratch) - inch rear tires 33psi car 19" tires 28psi It's not that bad...it really should pump air at higher pressures right? after 14 minutes it was at 35psi "prime the pump" when it takes 14 minutes to pressurize 7psi? Since then you have to let it cool down before doing the other 3 tires. You would spend half a day doing that to "inflate" tires. They really need to rebrand this product or take it off the market. It works well as a motorcycle tire pump but is completely useless as a refill pump.