A straight bulkhead union in AN3, sized for the small-bore lines used in brake, clutch and instrumentation plumbing. It mounts through a drilled panel and is retained with a bulkhead nut on the reverse face, so the panel carries the load and the line is properly anchored either side rather than flexing through an unsupported hole. This is the correct way to route a line through a firewall or boot bulkhead, and it is normally what a scrutineer expects to see on a competition car. Stainless construction handles exposure to water, salt and brake fluid. Check the shank length against your panel thickness and deburr the hole before fitting.