Product review (4 stars): braze on piercing service valves.
everything arrived ok, good price, no surprises. Much less chance of refrigerant leaks than the bolt on type. Brazes into pipe pretty easy. Just be sure to use exact size (3/8" on 3/8" pipe). Braze it, cool it with wet rag, test for leaks with 100 psi of nitrogen and then put the white o-ring and the center piercing valve in place and screw on brass cap to pierce the pipe (after the pipe cools off) MAKE SURE TO USE THE WHITE TEFLON O-RING. I have used 1/4" to 5/8" valves they work pretty well. I can't remember which size these were.