The 1/2" (17 mm) barb tee X 3/4" FPT is used for two-way layout connecting the drip lateral with .700 OD (17 mm) to a PVC pipe using a PVC tee with 3/4” MPT. By using a double barb, the tubing is pushed over the barb for a very tight fit. Use for a layout of drip tubing or drip line.