BIRKENSTOCK. 1020550 1020497. BOSTON VEGAN. BLACK. The signature slip-on clog from BIRKENSTOCK - the Boston. A casual-wear staple that is perfect all year round with a simple adjustable design and contoured cork footbed that forms to the shape of your foot. The color-coordinated outsole rounds off the shoe s look of sophistication. Available in vegan materials including an upper made from the skin-friendly hard-wearing synthetic material Birkibuc.