Foot Orthotics are either accommadative or Functional in nature.  Accommadative are softer and help reduce pressure for the insensate foot or some one that cant tolerate a functional foot orthotic. Functional Foot Orthotics usually have a firm arch and heel cup made of a polymer material such as plastic or carbon fiber.  They are usually covered by a spongy material to provide some cushion.  Functional Foot Orthotics will last longer just by the nature of the material they are made out of.'