The 1/4" barbed tee is used to connect three ends of 1/4" micro tubing or extend and branch two lines of micro tubing from 1/2" or 3/4" drip tubing. It will also work with tubing that has an ID (Inside Diameter) of .140 to .170.
Use a punch to make a hole in the larger tubing and this fitting is inserted in the hole and the microtube is pushed over the other ends of the barbs.