This plastic 4-way mainline entrance comes in three sizes to fit 1/2″, 3/4″, and 1″ plastic mainline tubing. This fitting has hose barbs on both ends to install in the mainline tubing like a coupling with 4 entrance ports for 5/16″ plastic lateral line tubing. The entrances are at a Y angle to improve flow. Also known as 4 way mainline tees. Hose clamps should be used on the plastic mainline, over the barbs to make certain the fitting seals and does not pull apart. Plastic caps should be used on the unused entrance ports to seal the system from leaks.