The Chirp Extreme Relief 3-Wheel Pack includes a 10″ Acupressure Wheel designed to massage pressure points around your spine while also provding a 4-way stretch. It also includes a 6″ Knot Kneader Wheel that mimics a kneading motion on the soft muscle tissue surrounding your spinal while offering an intense stretch. The 4″ “Tech Neck” Relief Wheel is designed to apply gentle pressure to the suboccipital trigger points in your neck . loosening your neck and upper back muscles that are strainted due to excessive neck strain from cell phone and monitor screens. The Chirp XR 3 Wheel Pack includes a 10 year manufacturer warranty against defects. Each wheel can support up to 500 lbs.