The soles of Fitkicks shoes, Sidekicks shoes, and Kozikicks shoes are each different. Each shoe is meant for a different purpose. To help you understand, here is more detailed information on each.
The Fitkicks sole is made from a PVC and mesh combination that the manufacturer terms Flex Form technology. The soles are soft and pliable but still sturdy, and they form fit to your feet over time. The Fit kicks are made to be worn indoors or outdoors for casual activities and may get wet.
The Sidekicks sole is made from vulcanized rubber thick enough to withstand outdoor/street wear. These shoes are made for relief from high heels, but also for dancing, commuting, and other light activities. They can be worn indoors and outdoors. The soles can get wet but the uppers are not meant to.
The Kozikicks sole is made from rubber with gripping nubs to help prevent slips. It has the same Flex Form technology as the Fitkicks shoes but is thicker. These shoes are meant for indoor and outdoor wear so that you can keep moving throughout your day without pausing to change your shoes. The soles will protect from wet surfaces, but due to the plush lining the uppers will be slow to dry if they get wet.