Birkenstock Arizona "Soft Footbed" Birko-Flor Sandals, Basalt, 38 M EU (US Women Size 7-7.5) Birko-Flor - a synthetic material made of acrylic and polyamide felt fibers that is comfortable and tear resistant. Imported Soft Footbed features an extra layer of cushioning foam built into legendary Birkenstock footbed. Birkenstock Arizona Birko-Flor Soft Footbed Sandals, Basalt (a Dark Grey/Blueberry Blue like color), Unisex, 38 M EU (US Women Size 7 to 7.5 or US Men Size 5 to 5.5) Anatomically correct cork footbed that is both renewable and sustainable. Birkenstock Arizona Basalt Birko-Flor Upper; Unisex Sandal. Arizona from Birkenstock is a classic two-strap style with fully adjustable straps and shock-absorbing EVA sole. Made by Birkenstock Germany.