Strappy Birkenstocks with a classic molded footbed and Birko-Flor uppers Birko-Flor is a signature leather-like material lined in soft felt, for an immediate broken in, comfortable fit. Crisscross straps form a toe loop, with a third strap over the instep adjustable with buckle detailing. Sizing Tip: This style runs true to size. If between sizes size up.