I recently bought the L/XL K9 Sport Sleeper for DeVito . He's about 19 inches from neck to base of tail , so it was plenty big for him. He loves laying on it vs hardwood floors at home. I also ordered the S/M size to put inside his Sports Shack . We use it for our SNL "city camping" . He loves going inside and curling up . It's very well made , inflates and deflates quickly and easily and rolls up small enough to take anywhere you might want your doggo to be more comfortable .