Foam roller that features hollow core design and patented multi-density foam surface to deliver firm compression on tight muscle, knots, and kinks to help increase muscle flexibility and mobility Proprietary Distrodensity surface pattern replicates the feeling of a massage therapist’s hands, helping to relieve tight muscles and enhance recovery Featuring the patented hollow core design, the GRID retains its shape after repeated and frequent use Wrapped in durable EVA foam, the roller is firmer than traditional foam rollers and easy to wipe clean Measures 13" x 5.5" and weighs 1.32 lbs.