Plantar fasciitis it's one of the most frustrating, painful injuries a walker or runner can have. The Pro-Tec Spiky Massage Ball is a studded massage ball that can be rolled under the foot, applying pressure to the tissue and muscles on the underside of the foot. That targeted deep tissue massage helps to increase blood flow, stimulating recovery and relieving the symptoms of plantar fasciitis. The ball is 3 inches in diameter.