The outside of the K&H Self-Warming Pet Lounge Sleeper is in poly/cotton and the inside is lined in soft micro fleece. The pillow has a layer of metalized insulation that radiates warmth generated from the pets own body heat. The K&H Self-Warming Pet Lounge Sleeper is a cozy lounge bed that every pet will love. The K&H Self-Warming Pet Lounge Sleeper is completely machine washable and filled with premium polyfil made from recycled plastic bottles. The bottom of the bed also has a layer of "stay put" non-slip fabric for stability.