Birkenstock Stylish 'Gizeh' Birko-Flor Women's Thong Sandals, Matte Black Upper material: Birkenstock Birko-Flor - a synthetic material made of acrylic and polyamide felt fibers that is comfortable and tear resistant. Imported Rubber sole Platform measures approximately .50" Experience maximum comfort in this modern gladiator-style thong sandal. Birko-Flor is made of acrylic and polyamide felt fibers with a leather-like texture on top and a soft fabric underneath against the skin. Please note: Birkenstock makes the Gizeh Sandals intentionally roomy for added comfort so they tend to run large. Most people prefer it this way since the buckles can be adjusted for a tight fit. However, if you prefer a very tight fit AND do not plan on wearing socks: we recommend purchasing a size smaller than you typically purchase. For example, if you normally purchase a size 38 M, we recommend purchasing a size 37 M. The letter "M" indicates "Medium/Regular/Normal Width Footbed". The letter "N" indicates "Narrow Width Footbed". **** Product update: newly updated model (latest production 08/2016); Arizona may now ship in newly designed Birkenstock shoe box (new blue shoe box design with handy size measuring guide printed on inside of shoe box). Sandals may now also come with black (not yellow) lettering on footbed. Original white shoe box design and yellow print will be gradually phased out. ****