A shoe is an item of footwear. Shoes may vary from a simple flip-flop to a complex boot. Shoes may have high or low heels, although in western cultures, high heels are considered a women's style. Shoe materials include leather or canvas. Athletic shoe soles may sometimes be made of rubber. Most of the shoes make use of the leather as their product for making shoes. Most commonly the soles in many shoes are made up from leather which increases the life of the shoe. The outsole is the layer in direct contact with the ground. Dress shoes have leather outsoles; casual or work-oriented shoes have outsoles made of natural rubber or a synthetic imitation. The outsole may comprise a single piece, or may comprise separate pieces of different materials. Dress shoes are categorized by smooth and supple leather uppers, leather soles, and narrow sleek figure. Casual shoes are characterized by sturdy leather uppers, non-leather outsoles, and wide profile.