From Klinik RC:
The Racetec RC Nitro Engine Compression Gauge makes checking the health of your engines a breeze. Check the health of your engines in or out of the car quickly and easily, document your engines wear and find potential problems with reliability or performance in seconds. Compression is a basic test of any engine from the car you drive to atv’s and now in RC engines. The compression gauge will fit any RC engine with a turbo style glow plug.
Requires 2x AAA batteries