This ankle bracing sleeve has K-Zone technology which provides Medial and Lateral stabilization, treats ankle weakness and Achilles tendonitis. The thin profile of this sleeve fits under any apparel. Choose a left- or right-foot shape specific size, one per package.OS1st has greatly improved upon the light bracing base layer that can be worn during any activity or sport, such as running or hiking, for added support and compression without compromising comfort and flexibility/mobility. Their compression zone technology mimics kinesiology taping techniques and combines the benefits of medical grade orthopedic support with graduated compression. The material is highly breathable and thin enough to not be restrictive or cumbersome during activity. Get back out on the Eastern Sierra trail quicker post-injury with an Os1st bracing sleeve!