The FM300 and FM300B Foot Rockers, with their ball bearing rollers, encourage users to move more by rocking their feet. This rocking motion uses the lower leg muscles to increase healthful circulation. The FM300B offers built-in massage balls to rejuvenate tired feet. In addition, both Foot Rockers offer three-inch height adjustment for custom positioning. Our Foot Rockers also raise the feet to relieve pressure on the lower back when sitting.