The BackJoy SitSmart is an innovative, proven sitting device that provides natural, safe and effective back pain relief by optimizing your postureanytime and anywhere you sit. Its easy-to-use, patented design works from the bottom up by tilting your hips upright and floating your spine in a comfortable cradle above the sitting surface for posture support and pain relief. Its portable and lightweight design works in any seat so you can feel more comfortable, supported and less fatigued after sitting for long periods of time. Works on any seat type, hard or soft, including office chairs, sofas and car seats. Durable (and waterproof) base and covering provide long-term use. Fits adults 100-300 lbs. SitSmart is designed to cup the pelvis itself, not the soft tissue around it. The standard size fits nearly all adults regardless of weight or height.