Device Description: The Reservoir Dog Check Valve has 1/8" NPT threads male and female. The housing is bored out to allow a press fit of the little rings, with the stainless steel ball captured in between. The upper ring is designed to seal against the ball during inverted flight, while the lower ring has small upsets in it to allow the brake fluid reservoir to breath during normal flight. It will prevent hydraulic fluid leaks in any inverted flight attitude, except for possibly a long, sustained, steep (30 degrees or more) inverted climb, not something too many planes are capable of.
Exploded View of the Components: