[blam]

So...because of tradition, we still call the 20 pounders but they're really 15 pounders, eh?

Thanks, I didn't know that.

[DuncanWaring]

I don’t know about the “weight” rating, but when I get mine filled they take about 4.5 gallons.

Also, once they are 12 years old, they can’t legally be refilled, but if you find one that’s 11 years old, you can probably get it for a good price (”It’ll be unfillable in a year - only good for scrap metal - give ya a buck for it.”), fill it one last time, and store it.