Swede-O Thermal Plantar DR has a rigid strap that pulls the foot into some dorsiflexion. Thermal properties reduce inflammation, and with the stretching of the plantar fascia during sleep, this soft boot may aid in the recovery of Plantar Fasciitis. Measurement is based on your shoe size Size Chart X-Small Mens 3-5 Womens 4-6 Small Mens 6-7 Womens 7-9 Medium Mens 8-10 Womens 10-11 Large Mens 11-12 Womens 12-13 X-Large Mens 12-14 Womens 13-15