Birkenstock Zermatt Slippers. The Zermatt is Birkenstock's first true slipper. It features their iconic cork latex footbed, and to keep you extra cozy, it's fully lined in genuine shearling that will keep your feet warm all winter long. The upper consists of soft genuine wool. Anatomically shaped cork/latex footbed lined with shearling. Wool felt upper. Cork footbed material: Cork is a sustainable material extracted from the bark layer of the cork oak. This natural product is insulating and offers very good cushioning. Imported.