Birkenstock Gizeh BS Regular Fit Onyx (Metallic Gray ) Size Women 11 Mens 9 The Birkenstock Gizeh BS Regular Fit Onyx sandals in metallic gray size EU 40 are a stylish and comfortable choice for casual occasions. These flat sandals feature a sleek design with a metallic black/gray color and synthetic upper material. The Birkenstock brand is known for its quality and support, making these sandals a practical and fashionable option for women who value both comfort and style.