Nalgene 32oz Fuel Bottles....
And for us really old-school MSR users, there were Sigg aluminum bottles, which is what MSR originally built their stoves to use. The problem was that when pumped up to high pressures the Sigg bottles sometimes failed, as they were designed for storage, not necessarily to be a pressurized tank. So MSR came out with their own supposedly more robust bottles. (And also to capture that revenue stream.)
I still have, and use, my MSR XGK stove from 1987. Not very high tech by today's standards, but what other backpacking stove can double as a welding torch too?
Anyway, unasked-for history lesson over :-)