The GRID X® Foam Roller is our firmest foam roller. It was created to break through the body’s toughest, tightest trouble spots to improve mobility and reduce muscle pain and soreness. This extra firm foam roller is for athletes with dense muscle tissue and anyone who prefers a deep tissue massage. Dense tissue needs a firmer GRID foam roller to release and relieve aches and pains. The GRID X can be used to release the calves, quadriceps, hamstrings, back and lats.