HSA/FSA EligibleDesigned for those who want to massage their plantar fascia areaTherapy for your feet: soothes muscle soreness and helps increase circulation Can be filled with hot, cold, or room temperature tap water. Use cold to reduce inflammation. Use hot to reduce soreness. Nubbed and smooth. The nubbed section provides a stimulating massage as you roll the ball back and forth under your foot. The ball also comes with a sure-grip band for easier grip on smooth surfaces while creating a gentle massage.