16S blanking pug with oring

For closing off a hydraulic connection, the 16S blanking plug with an O-ring is meant to seal the opening and help prevent leaks. It is sold as an Adaptall part under supplier part number SS5204P-16.

Blocking off an unused hydraulic port is exactly what it handles. The o-ring built into it creates a seal against fluid leakage, so you are not just putting a dry plug in a hole and hoping for the best. If you have an open port on a manifold, valve block, or fitting that needs to stay closed and leak-free, this is the part that takes care of it.