They are like the SSR mattresses - no bar. They seem about the same size as the bed in the studio. I ended up on one for a night during my last trip (I was alone with DS11 and DD9) - both kids decided they wanted to sleep in the bed with me and it did not take long for me to realize that it's like having three grown people in a bed now that they are bigger!
So - I moved to the pull-out in the middle of the night. I actually thought it was very comfortable - and my back had been bothering me prior to the trip. It was 10X better than the mattresses at POP!!!
One warning - there is NO floorspace once the couch is pulled out - we were stuffing the cushions under the bed, on top of the wardrobe

Seriously.