WHY YOU NEED A AIR GAGE: A reasonable inflated tire save fuel, increase the tire's lifespan, improve the driving experience, and insure the driving safety. Please use tire gauge to test the wheel pressure every week regularly when the tire is cold, especialy before long distance travel. ACCURATE GUARANTEE: Our 10-100PSI tire pressure gauge passes the specified test and calibrated to ANSI B40.1 Grade B (2%) international accuracy standard. You can get a precise tire pressure for your tires and decide to inflate or release the gas, without driving to gas station or garage. For sedan, 28-35PSI is perfect.EASY TO OPERATE: Press the air bleeder button, turn on the tire valve cap, insert the tire pressure air chuck tip, read the tire pressure from 1-5/8" dial after the pointer stop moving. You also can get the tire pressure after taking off the air chuck tip from the tire due to the pressure holding function. No battery needed.Over-inflated tires have long braking distance and are easy to slip on rainy days, also the middle part of the tire will wear too fast. Under-inflated tires need to consume more fuel while driving, not good for purses and the environment. A resonable inflated tire save fuel, increase the tire's lifespan, improve the driving experience, and insure the driving safety.