These gauges are for use on K-Class (Kitchen) fire extinguishers only. Gauges for other types of extinguishers are available separately.
The Extinguisher Gauge Wrench (item # 09838) makes installation and removal of gauges a snap, even in tight places.
Note: Gauges are calibrated against atmospheric pressure, which is indicated when the gauge reads zero. Thus, a cylinder pressure of 100 psi would move the pointer to 100. If there is a slow leak inside the case, however, and the pressure inside the *gauge* was 100 psi, the gauge would read zero. New gauges such as these have pressure relief devices which relieve case pressure at 50 psi or less. There are many ways of creating leaks and leaks are not the only things that cause gauges to give false readings, so care should be used when installing them.