Adding soles to the sandal has been a process over decades; we tried so many different materials, rubber, gum rubber, laytex, rubber tires, ground up rubber, bicycle tires.  

After a few years, we found some super light and flexible material, which helps keep the idea of the original sandal in tact.  The original sandal feels like nothing on your feet, we attempted to emulate that.  We have gotten as close as we can, sandals with sole are flexible and light.  This sole acts as a water blocker and gives a little sturdiness. 

Currently we use many different types of soles, some we have made ourselves.