I have been looking at trifold mattresses for my 2013 prius for a while for my wife and I to car camp at the beach this spring. From the reviews I had read I knew I was going to buy a Milliard brand but wasnt sure if I wanted 4" or 6" though. Well pulled the trigger this morning since Amazon has the Milliard premium trifold 4" full mattress for $105 with free ship right now. From what im reading the difference in the premium and regular milliard trifold is the premium has a removable waterproof cover while the regular does not and possibly more memory foam as well? it shows the mattress can be flipped with one side softer and one firmer side. I also purchased the carrying case which I believe was $24 to keep it clean and transportable when not in use. Link is from my affiliate amazon page but i have no affiliation to Milliard. Hopefully it will help someone out there looking for a two person mattress for their prius or prius V as this is by far the cheapest I've seen for these. Not sure if they have any deals on the single person size but the full is supposed to be a perfect fit for the back of a prius. Mattress https://amzn.to/3ssxz2m Cover https://amzn.to/3K3S7nt
It always confounds me that people sleep in a Prius in the back with seat down on such an uncomfortable surface when you have so much padding in the seats if you slide both front seats all the way forward and remove the headrests and recline the seats flush with the back seat. I also pulled out my center console and replaced it with a pillow. Makes the whole inside of my Gen2 prius like a giant bed and no need for flimsy over-priced Amazon "mattress."