J Fit 36-Inch Extra Durable Hi-Density Foam Roller Hi Density Foam Rollers are extra firm and will last much longer then White single construction foam rollers. This foam roller is 36" in length and 6" in diameter. It can be used to enhance balance, body awareness, muscle re-education, flexibility, myofacial release and dynamic strength. Dense foam construction of rolls provides firm support for all body types. Foam rollers are an essential tool for Pilates core abdominal, back stabilization and strengthening. Foam rollers are used as a balance training tool to improve balance for sports and everyday exercises. They are also an excellent aid for self massage of the upper and lower back, calf, hamstring, glutes and quads.