An AN6 tee with male 37° flares on the through run and a rotating female swivel on the side branch. AN6 is the default size for most performance fuel systems, so this is a frequently used fitting — splitting a feed to twin fuel rails, merging returns, teeing off to a pressure regulator, gauge or sender, or branching an oil or coolant circuit. The swivel side means the branch hose can be angled correctly without stressing the tee or the line. Fit the run first, then set the branch. Support the assembly so its weight is not hanging off a single threaded port.