Monster Fitness Black High Density Foam Rollers - Extra Firm Molded polyethylene foam technology has a 2 lbs. per cubic foot density, Smooth surface. Built to hold up to the most rigorous and demanding foam roller applications, Will not lose its shape after moderate to heavy use. Perfect for developing core stabilization, lower body balance and stamina, excellent for pre/post workout. Built to hold up to the most rigorous and demanding foam roller applications, providing maximum firmness, Sturdy and resilient. May also be used for gentle stretching and self-mobilization of joints and spine