First of all, YOU MUST LET THIS MATTRESS SIT OUT FOR 24 HOURS after removal from the box. Or, you can be an idiot like I was, and email the company and tell them the mattress isn't the size it was advertised to be! lol! I measured it at a short 45" when I took it out of the box, and was very upset. However, after they replied and told me what to do, it did indeed expand to the correct measurements. (It even expanded with my dog laying on it, which I thought was pretty cool!) So be sure and read the instructional insert that comes in the box.We bought this bed for our 68-lb. mixed breed, Piper, who will be 15 in April. She has arthritis in her back, and her back legs are weak. Prior to finding this bed, she was laying on the cushions from our love seat that we laid out on the floor for her. They were deep, though, and she was starting to have trouble getting "out" of them. So we wanted something less soft, and less deep. This mattress looked perfect. And judging from how she is sleeping on it, and laying on it most of the day, I would say it is.A couple of negative reviews on here were with regard to the waterproof lining that really wasn't/isn't waterproof. I think if you trust waterproof linings, and they don't work, that's really on you. With dogs, you always need to put extra safeguards in place. I also don't want to be washing this cover if she has an accident; I want it to stay beautiful. So here's my solution, and how we have it set up for Piper: the mattress is covered with a blanket. On top of the blanket, we have waterproof crib pads from the baby section at Wal-Mart (you can get waterproof baby stuff in all different sizes, which is wonderful), and on top of that, we have a really soft gray throw that's tucked "in" so it looks very neat. This will solve the "is it waterproof or isn't it" with the inner lining. It will also keep the padding from having dog odors just from laying on the cover with no other covering on it. (And the crib pads DO work. When a 68-pound dog pees, it's a lot of pee, and these pads have caught them all, after being partially absorbed by the blanket.I highly recommend this bed for any dog to sleep on, especially large dogs. The covers (you get two) are sewn so nicely that I had trouble finding the zipper, as it's hidden under a seam. The mattress is very firm, and not made with cheap foam. This is definitely memory foam.The mattress shipped the same day I ordered it. I can't say that will always happen, but I was thrilled. My email was also answered promptly, and courteously, as were all of the follow-ups.In closing, if you're thinking of a bed for your dog, this one is top of the line.