The size it's small, I ordered the size L and it quite small. The gel pad will not work for long hours outside during the summer as you have to keep putting it back in the freezer. It can be used just as a regular bed.

The bed is awesome and my dog loves it, but it runs very small. You should order a large or extra large for a medium dog.

I have 2 Cavalier King Charles spaniels, both tri-colored, so they have a lot of black coat. Also, this breed is brachycephalic...short snout that creates some breathing problems. Found out the hard way that long summer travel is challenging with these guys, and they overheat easily during hot weather travel pit stops. Took a chance on this product because of the bolsters (which my boys love)... before the next summer car trip...and we were extremely pleased! Purchased 2 large for the back seat of a Ford Explorer, and a medium for the front passenger seat (pups gotta have seating options!) REALLY helped to cool them down. Like magic! So happy. Inside, covered outside, the rare crate containment...my boys clearly like these beds when they’re hot. Great find! Also, bolsters are 4 1/2 inches wide so add 9 inches to width and length for actual size.

I bought the L bed for my german shepherd dog (90#) and it is like a medium sized dog bed. It is way too small for him. It's the perfect size for my Australian cattle dog (50#)