When you're driving, your own safely and that of your friends and family are riding on your tires. A small investment in a pressure tester will give you the assurance that you're tires are well balanced and won't pull your car to the left or the right as you drive. Pressure testers measure the amount of air in your tires. Too much or too little could cause, at best, problems while you drive and, at worst, a blowout. A cheap pressure tester is all you need, so keep one in the glove box and check your tires at least once a month when you're at the gas station.