swamp diver
Contributor
Keep in mind that stainless and aluminum are not the best materials if you plan to do anything with oxygen or rich nitrox mixes. Brass is your friend in those cases (you'll alway want to be careful with sealing surfaces and any lubricants as well).
As Wookie stated it is very hard to find brass fittings rated above 3000 psi. All our nitrox and pure oxygen system are plumbed with stainless 316 tubing and fittings.
Lately we have purchased some difficult to find fittings SAE (ORB) to NPT elbows from Stainless Steel Fittings | Compression Tube Fittings | Stainless Adapters and received good service. The fittings were actually made in Ohio by Airway manufacturing and an identical copy of the Parker dimensions plus less than half the cost.