3" thick orthopedic foam. Topped with an extra layer of polyfill fiber. Extra-deep sleep surface. Low-profile front and back bolsters. Machine washable cover. Designed for dogs that love to nestle under the covers or beneath piles of pillows, our Sherpa Pet Den is topped with a raised hood that satisfies your pet's instinctive desire to burrow. A plush polyester lambswool cover keeps them warm throughout the year. . . . . .