Featuring a hollow core design, the TriggerPoint GRID Foam Roller is composed of a patented multi-density foam surface to deliver firm compression on tight muscles, knots, and kinks. The proprietary Distrodensity zones replicate the feeling of a massage therapist's hands, which help promote the flow of blood and oxygen - the key nutrients needed to repair muscles. Ideal for beginners to advanced rollers, the GRID Foam Roller releases muscle pain and tightness, improves mobility, and increases circulation to help users move and feel better.