The Chirp Wheels are made with a rigid ABS plastic core and soft EVA compression sensitive mat so that the wheel can support up to 500 pounds! Rolling out on the Chirp Wheel will help decompress your spine, strengthen core muscles, and relieve pressure on the spinal cord, resulting in reduced back and neck pain. It can also stretch sore muscles and provide a deep tissue massage therapy. You can also apply different levels of pressure with the 3 sizes included. The smaller the wheel, the more targeted the pressure, allowing the user to target specific muscle knots. The larger the wheel, the greater opening effect in the chest.