That brings up an interesting question. Why was 5/16 settled on for tubing size? Suspicious minds gotta wonder if it's ONLY because it's an oddball size, and tees, adaptors and other fittings are not readily availble EXCEPT from maple dealers. I can get 1/4 and 3/8 fittings anywhere, but never 5/16. I asked a dealer once and he just chuckled and said "Why do you think?"