Pro-Tec Athletics offers Hollow Core Foam Rollers, available in contoured or smooth styles. The contoured high density foam roller features raised sections—long ridges and pronounced bumps—to stimulate blood flow and allow for a customized deep massage. The flat surface of the smooth foam roller allows for a smoother and faster roll. Both smooth and contoured rollers feature a hollow core for improved durability and a thin outer layer of foam that provides a firm surface for aggressive massage. With a 5.5″ diameter and 13″ length, the rollers can accommodate large and small muscle groups.