When doing a 3400 intake manifold swap on a older 3100 engine, you need to convert the threaded heater hose setup that came on your car to the newer slip-fit style on the 3400. This tube gives you the quickest, easiest, and cheapest way to do that, without having to go through of drilling and tapping your new 3400 manifold for 1/2" NPT. Unlike most 3400 tubes that have a quick-disconnect fitting on the other end of the tube, this tube is made to have traditional heater hoses slip over the tube and have a bead to seal on.