Birkenstock Sandals Gray / Black 3 Strap Birkis Narrow Size 37 US 6 These Birkenstock Birkis sandals are perfect for any casual or travel occasion. The slip-on style and adjustable straps make them easy to wear with any outfit. The suede upper material and flat heel style provide comfort and support for all-day wear. The gray and black color combination is versatile and can be paired with any outfit. These sandals are available in a narrow size 38, which is equivalent to a US size 7. The Birkenstock brand is known for its quality and durability, making these sandals a great investment for any wardrobe.