The OTC Digital Compression Gauge Head and Boot can replace analog gauges to provide advanced features, including measure, record, and playback of compression readings on up to 12 cylinders for quick testing and diagnosis. The gauge head can directly replace any 2-1/2" analog gauge with a 1/4" NPT male thread. Upgrades current compression gauge with exact numeric measurements. The digital gauge is easy to read and can display pressures in psi, kPA, bar, and kg/c. A convenient push-button side release valve relieves pressure for repeat testing.