Correct gas bottle ratings for RVs?


I've just been informed that there are ratings on gas bottles, from 1 to 4, with 1 and 2 apparently being suitable for RVs.

I was told that insurance companies will wipe your claim if you have the wrong rated bottles.
The rated number is in a circle on the neck of the bottle. I noticed that most bottles you get from swap-and-go type places are a 4. Is there any truth in this?

Will Schonewille, Qld