But it's expensive for what is basically a special shaped sleeping bag. $300 and they don't even say what thread count, but you can "upgrade" to 200 or 300 count for even more money. We use a fitted sheet my wife modified from a queen sized sheet to fit the v-berth (we have 2 so we can switch). It's a PITA to make the bed (especially at the foot). A light cotton knit blanket and standard top sheet for warm nights, plus a heavier microfiber throw do the trick for us when it's cooler. That's way cheaper, and easy to wash or replace only what's needed.

We've used a sleeping bag in the past (as a throw) and that works OK too, but we didn't sleep inside it because only one side is zippered and either occupant needs to be able to throw off the blanket (from one side) when it's too warm.