Mine is 3 inch pvc, probably 30-36 inches long, but I can measure it. I bought bio-balls (for aquariums) as opposed to wiffle balls. I think wiffle balls are just as good most likely, but a few people have said that bioballs are better. I was lucky enough to have a good relationship with my compressor guy who builds professional quality nitrox sticks. He offered to plumb mine the way he does his metal ones. So after I made it, he tapped in the line coming from the dwyer needle valve into the stick. He also added his custom oxygen sensor holder so the unit sits on the stick, as well as added an oxygen solenoid that cuts off when the compressor does, and a overpressure device so backpressure can't build in the oxygen line (which I didn't know was a thing). I believe it looks identical to Ray's except my stick is PVC. He also added a plastic brillo scouring pad on top of the bioballs. He said he likes the gas to go through a small area of smaller holes first then through the balls. The stick works flawlessly and needs minimal adjustment. Usually only adjustments are needed when the supply bottle is low and the oxygen reg isn't working perfectly.
I actually am in the process of buying a used Tri-Hunter 6000 for my Trimix needs. I was going to build a second stick and connect it to my current stick, so the first stick would mix helium and the second would add the oxygen. But then you have to figure out the drops in 02 levels on your sensor which coordinates with helium levels. The Tri-hunter I'm getting is at a very reasonable price, so I decided it's worth the money to not waste time doing it myself. I'm actually a little sad to not be using my nitrox stick anymore. I plan to hook up the Tri-hunter and run it for a little while to see how it does with Nitrox alone compare to my current stick. If it's not as "set it and forget it" as my Nitrox stick then I may actually just keep both on the wall, using mine for Nitrox (which is 95% of my fills) and the Tri-Hunter just for trimix. Then I'd have to find a way to have both simultaneously attached to my compressor inlet. I'm thinking a y-shaped ball valve that allows both sticks to feed into the main intake line, and then I can just shut off the side I'm not using with the ball valve. Good news is I talked to Wayne who builds the Tri-Hunter and he was telling me he turns on his compressor and then drives around town doing errands for a few hours, and comes home to a filled bank that's 100% on point. So I'm hoping the Tri-Hunter works as expected. I know Wayne personally and know he's not full of bull about driving away for hours. I don't know that I'd get the same accuracy though, since I'm filling a smaller amount.
If it works as well as I hope, I may be selling my Nitrox stick FYI
