The surface of the RumbleRoller contains specially designed bumps that help continuously knead the contours of your body as you roll across it, helping to stretch soft tissue and increasing circulation. The RumbleRoller helps aid recovery from muscle pain, erode muscle knots or trigger points and increase flexibility. If you need the deepest and most effective foam rolling experience, look no further than the RumbleRoller. � Waterproof and latex-free urethane construction� Non-porous surface with anti-microbial additive that prevents bacterial growth� Available in firm or extra firm and in two lengths