This mobility ball can be used all over the body. Bottom of foot for plantar fasciitis, shoulder blade for shoulder impingement, and TFL for hip and knee pain. This is a standard lacrosse ball, which are used in clinics for self tissue mobilization. 
 
If you are unsure of how to use your mobility ball for your feet and want to restore your foot shape, check out the Foot Health Kit for a complete guide to foot restoration.