The blue insole uses the same principle as walking barefoot and was designed on the basis of the footprint left by a healthy foot on the sand. In this way the natural condition of foot support is recreated. The heel area is adequately cushioned and stabilized thanks to the enveloping shape. Furthermore, the natural plantar arches of the feet are suitably supported. The blue insole is therefore the ideal solution for those who do not want to give up the exceptional BIRKENSTOCK comfort even in closed shoes from other brands.