This is a product that everyone who owns a car should have in one form or another. Most gas stations have a place to inflate tires with air, and most of these gas stations have a built-in pressure gauge that you can use, but having your own pressure gauge is much easier and more convenient. It's relatively compact, but there's some variability depending on the angle at which you check tire pressure. Since there are measurement errors, you often have to make several attempts at different angles to get the right reading. The tire pressure is never overestimated, the maximum value reached is the actual tire pressure.