PFO- prepared for orthodic. This sandal was designed from the countless people over the years that have to wear orthodics, and cant find some cool orthodics that they like wearing. we designed a recycled cork/rubber insert with a company that does medical inserts, trying to find the best most comfortable insole we could make. it is our comfort walking sandal, not to be confused with the original jc. also with super flex vibram sole. *important note, this is a re-worked slip, it is nothing like the original slip-on, only in appearance, it is taller, heavier, and contains more rope. the insert will not fit in our regular slip as we had to build a cup and adjust straps for the insole.