BIRKENSTOCK. 1017 539. ZERMATT WOOL FELT SHEARLING SLIPPER. DARK BLUE. The perfect slipper from your favorite brand has arrived introducing the Zermatt Wool Felt Shearling slippers from Birkenstock. A cozy one-piece wool felt upper delivers a moccasin silhouette with cradlng comfort and can be worn all year round. A genuine shearling footbed allows for warmth without overheating and absorbs sweat. An anatomically shaped footbed provides support while a latex sole provides traction.