A softly inflated flexible disc used in chair seats to prevent fatigue, reduce pressure on the tail-bone, and help relieve lower back pain, while strengthening the core muscles and improving posture. The Sit Upon can be used on hard or soft chairs, recliners, car seats - anywhere you sit for long periods of time! The Sit Upon should be placed in the chair with its smooth side facing down. The side with knobby texture allows air flow for cooler seating and promotes improved blood circulation. Because it is filled with air, it will stay soft and comfortable, and "one size fits all"!