Just a reminder that all cylinders are not necessarily alike. Twenty-five years ago I discovered that (at least then) my ASW 24 oxygen bottle holder was a REALLY tight fit for a steel bottle (D size, IIRC; my LS-3 was sized for an E bottle--same diameter but longer). That's when I learned that aluminum bottles with the same nominal diameter (4.3") were slightly larger and composite bottles larger still.

I can't find much online to confirm whether that's still the case. Most sources just list diameter as 4.3". But several do confirm that aluminum bottles are 4.37" dia. (possibly because the wall thickness is twice that for steel bottles). No big deal if there's some clearance in the mounting tube or you're using a clamp-type mount. A non-starter if--like mine--the molded in fiberglass tube is a "perfect" fit after some sanding (of the fiberglass tube, not the bottle).

Chip Bearden