Birkenstock Boston Big Buckle in Black Dressy Leather. The BIRKENSTOCK Boston is a veritable classic that can easily be worn all year round. It has a legendary status thanks to its sophisticated, individually adjustable design. The Big Buckle version features a large, elegant pin buckle – a fantastic, striking eye-catcher on this otherwise understated sandal. The semi-exquisite footbed is fully lined with soft piumato leather, making it exceptionally comfortable. The upper is made from especially fine and high-quality Amalfi leather.