A three-way tee machined with AN10 male 37-degree flares on every port, so it accepts standard AN10 female hose ends or adapters on all three sides. It is the usual way to split a single large feed into two branches, or to merge two returns into one line, in fuel, oil and coolant systems. Common uses include feeding twin fuel rails from one supply line, combining dry sump scavenge returns, or teeing a cooler circuit. Because all three ports are the same size, plan the flow direction sensibly rather than assuming any port is a designated inlet. Reducing bushes or adapters can be fitted if a branch needs to step down.