1/4" bulkhead union allows a racer a safe way to pass thru a firewall, cockpit or capsule in the event that a 1/4" airline needs to be run in an area where an engine or transmission needs to be removed between rounds making the routing for the air line cleaner and safer.
Bulkhead nuts are adjustable and offer enough adjustment to go thru a .375" plate. Hex nuts are 11/16" and made from brass.
Fittings are sold each and are simple to use. Push the hose into the fitting and to remove push in on the plastic colored part while pulling to remove the hose. Fittings operate from vacuum to 145 PSI.