Has a semi-rigid strap that pulls the toes upward and the foot into a slight dorsiflexion position. This gently stretches the plantar fascia so it may heal. The combination of the thermal properties that help reduce inflamation and the stretching of the plantar fascia while sleeping may aid in the treatment of Plantar Fasciitis. Non-slip Safety SoleTM rubber grip bottom helps prevent slipping. X-Small Mens shoe sizes 3-5 Womens shoe sizes 4-6 | Small Mens shoe sizes 6-7 Womens shoe sizes 7-9 | Medium Mens shoe sizes 8-10 Womens Medium shoe sizes 10-11 | Large Mens shoe sizes 11-12 Womens shoe sizes 12-13 | X-Large Mens shoe sizes 13-14+ Womens shoe sizes 14-15 | XX-Large Mens shoe sizes 15+ Womens shoe sizes 16+ .