EXELAIR by Milton (EX448DIG) Digital Tire Tread Depth Gauge ACCURATE: Performance-tested and calibrated. Measures/reads tire tread depth in both inches and millimeters (range: 0 to 1 inch, 0 to 25 mm). SAVE MONEY: On fuel cost and consumption. PROTECT: Yourself, your passengers, and your vehicle. EASY PUSH: On/Off (on the left) and Zero (on the right) buttons. Zero/Tare setting at any depth. Digital display screen for accuracy. CAR SAFETY/MAINTENANCE: Ideal automotive and road trip accessory tool to maintain optimal tire care and prevention. Proper tire tread is key to good road traction. These make great gifts for those you care about. AUTOMATIC SHUT-OFF: Features an auto shut-off to save battery life. Battery included.