HART Myotherapy Roller 15cmHART Myotherapy Rollers feature a "H" design which aids in spinal alignment when releasing paraspinal muscles. The pimple surface on the roller adds comfort to body rolling and releasing trigger points helps to reestablish proper movement patterns to enhance performance. 15cm model provides a smaller alternative to traditional foam rollers to pinpoint smaller muscles. Firm, solid, lightweight EVA foam. 15cm diameter. Foam Density Hardness: 50 35.