No more guessing if your tires are properly inflated - just look at valve cap
Automatically displays 'green' for proper inflation for 32 PSI; under-inflated turns red
Extend tire life, increase gas mileage and improve vehicle handling & safety with proper inflation
Set of 4 universal screw-on valve caps; for car, SUV & truck tires with 32 PSI pressure requirement
Durable, weather-resistant ABS and clear acrylic construction
An ingenious vehicle safety tool that pays for itself by helping you lower operating and maintenance costs. Installs instantly - just replace existing valve caps with the Indicator caps; green shows proper 32 PSI air pressure, color changes when pressure drops to 25-26 PSI and full red marking indicates tire pressure has fallen below 23 PSI (use tire-pressure gauge when installing; Indicator caps do NOT indicate over-inflation). One-year warranty and Jack's Tool Shed worry-free Satisfaction Guarantee.

For Reading, Firing & compression pressures on Gas or Diesel Engines. The engine indicator, for determining operating characteristic of internal combustion engines, dates back to James Watt who as early as 1790 conceived an instrument for showing varing pressures within the cylinder of his engine while a through for many purposes, a knowledge of maximum combustion or compression pressures is sufficient for routine engine maintenence.
Maximum pressure indicators, prior to the introduction of the T-100, were based on balancing a known spring pressure against cylinder pressure and reading the spring deflection in pounds per square inch. The patented T-100, on the other hand, utilizes the "trapped pressure" principle, whereby cylinder pressure is "trapped" within a chamber and the pressure read directly and conveniently on a high quality bourdon gauge. This field-proven concept reduces the moving part of the indicator to a single light weight, high temperature resistance valve, thus eliminating springs, counters, pistons and other operating problems generally found in conventional maximum cylinder pressure indicators. The gauge is tested and is accurate within one percent. It has been designed and is built particularly for use with TOPGRIP INDICATORS.