No leather materials used in construction. Crocs™ states these shoes should fit very loosely. The sides of your foot should not really touch the sides of the shoe. Your toes should never make contact with the front of the shoe. Once you have centered your foot on the foot-bed: You should have about a 1/4 to 1/2 inch of space in front of your toes, behind your heel and when you lift the strap you should be able to comfortably get your finger between the strap and heel. This durable, non-skid, multi- purpose clog is selling to water-sports enthusiasts, hikers, medical professionals, food service workers and fashion consumers. Made of patented resin that softens with body heat, allowing shoe to mold to the foot for a customizing fit. Built- in arch support and a back strap for added stability. Removable back strap. Resistant to bacteria and fungus. Ventilation system that allows air and water to pass through multiple ports in side of shoe