Do not beware
Do not beware! The exact size specifications were exactly what I received and naturally fit like a glove!!! Having made my own extendable bed for a camper I bought 10cm firm foam and ordered the covers from these guys. The covers are nylon based which to be fair is great for a camper as when transformed to a bed I cover with a sheet. I can also wipe down when I spill a beer. Genuinely chuffed to bit and for the price they will definitely pay for themselves over the next few years.