The footbed of the birkenstock was created to shape and form to the form of your foot as time passes, so that you get just the right support, making them exceedingly comfortable. Options that come with a great birkenstock sandal. Besides the plastic design with the eva footbed, there is the classic and original birkenstock footbed. The birkenstock footbed includes first a leather lining, then layers of cork and latex, which cushions and absorbs moisture.