My husband just purchased a used RV for our Summer travels instead of renting cabins. The queen size mattress that was in the unit was horrible. Well enter the 
Dream 10 Inch Hybrid Mattress, Queen Size High Density Foam and Pocket Spring Mattress in a Box and we are in heaven. This mattress fits the RV bed perfectly. It is a medium density and is foam with individually wrapped springs. It came as a bed in a box and although it said 48-72 hours to fully expand - it was about one full day and a half. The mattress was firm, comfortable and surprisingly a good fit for the RV. No chemical smells and it has a nice breathable covering. I used a mattress cover over it to protect it and added sheets - perfect fit. I highly recommend this mattress, it's quality all the way.