TriggerPoint GRID foam rollers feature a patented design that offers a superior, multi-density exterior constructed over a rigid, hollow core that withstands repeated use while maintaining shape and integrity. The proven durability of the GRID has helped make it a trusted tool of physical therapists, massage therapists, athletic trainers and professional athletes. The GRID can be used to roll through tight muscles, knots and kinks to reduce soreness and improve mobility. Regular use of the GRID can provide benefits such increased flexibility, improved balance and mobility and preparing the body for peak performance. The distinctive, multi-dimensional surfaces of the GRID replicate the feeling of a massage therapist's hands - wide and flat like the palm, long and tubular like the fingers, and small and firm like the finger tips. The textured surface of the GRID helps to maximize the flow of blood and oxygen to heal tissue. TriggerPoint GRID foam rollers are available in three sizes and two densities. Regular density models include the original 13-inch GRID, the 26-inch GRID 2.0, and the 4-inch travel-friendly GRID Mini. The 13-inch GRID X features extra dense foam for working the tightest muscles. Purchase of any TriggerPoint GRID foam roller includes free access to an online instructional video library from the experts at TriggerPoint that illustrate the best foam roller techniques. 1-year warranty