Latex,rubber Features soft donut-shaped pillow for nighttime relief of pain associated with total knee replacement or arthritis Pillow is enclosed in breathable, seamless knit elastic sleeve Washable AliMed Side-Sleep Knee Pillow features soft donut-shaped pillow for nighttime relief of pain associated with total knee replacement or arthritis. Pillow is enclosed in breathable, seamless knit elastic sleeve that helps maintain pillow's position while providing soothing warmth to knee area. Not made with natural rubber latex. Washable. White. Sizing: Measure thigh circumference 5-1/2" above knee. Medium fits 17" to 18"