The popular Madrid silhouette is now available with a lightweight EVA construction. The sandals feature a single strap across the foot with a buckle fastening and orthopaedic footbed for optimum comfort.Narrow Fit. Featuring adjustable strap, cork/latex footbed, and shock absorbing EVA sole. Made from EVA Ethyl vinyl acetate, a non-toxic synthetic compound.Fit Your toes and heel should not touch the rim of your sandals while standing in them. The extra room is needed to perform the natural rolling motion of the foot without restrictions - just as if you were barefoot. Birkenstocks are designed to be roomy. When you first try your sandals they might feel big. Most people are fine with a regular fitting, but if your foot moves side to side when you walk and adjusting the strap does not help, a narrow fitting may be more suitable.