With Speedmaster tire deflators, you can quickly deflate your tires to low pressures, regardless of their size, all while monitoring the pressure. When the valve is open, the tire deflates. When it is closed, you get an accurate current tire pressure reading. Corrosion Resistant Brass/Stainless Deflator Tool Quality Bronze Bourdon Tube Gauge Design Ensures Accuracy is Not Affected by Changes in Temperature, Humidity or Altitude Fully Geared, Solid Brass Precision Movement Protective Rubber Gauge Guard Easy to Read Dial with One PSI Increments Thoroughly Designed and Tested to Ensure Accuracy Includes Protective Canvas Pouch and Instruction Sheet