Correct size

B.O. Plenty wrote:
The sizes may vary. My trailer has what they called a king size bed. No mention of anything special. I measured it then bought a standar king to replace it. I had to add 2 inches to each side of my frame but the length was the same. If you buy one of the popular foam matresses in a box, you can remove the cloth cover and cut it to any size you want with an electric knife. then reinstall the cloth cover. Much cheaper than ordering a special size.
B.O.

the "Standard" RV King is really an Olympic Queen. I did just the opposite of B.O. I cut a couple inches off each side of the plywood base and put in a standard Queen bed. I now have an extra couple of inches on each side of the bed to move around.

Can you just measure your base where the mattress sets and order accordingly?

The sizes may vary. My trailer has what they called a king size bed. No mention of anything special. I measured it then bought a standar king to replace it. I had to add 2 inches to each side of my frame but the length was the same. If you buy one of the popular foam matresses in a box, you can remove the cloth cover and cut it to any size you want with an electric knife. then reinstall the cloth cover. Much cheaper than ordering a special size.
B.O.

Try This link

Seems like a lot of variation, I suggest you measure your bed not the mattress

Your measurements are? IMO bed measurements vary slightly among manufacturers.