As you might have noticed SIDI footwear does not use leather. Instead SIDI footwear makes use of a synthetic material called Technomicro.
Technomicro is a composite microfiber material created from strands that are so fine that each one is less than one thousandth the thickness of silk. These fibers act like natural leather skin, but with the advantage of better strength, softer texture and lighter weight. Technomicro is also water-repellent, quick-drying, breathable and permeable to water vapor, making it an ideal material for shoe uppers. It is abrasion- and mildew-resistant, easier to clean than leather and resists stretching and deterioration from atmospheric agents.
Technomicro does not stretch, but it will begin to conform to a foot as it warms up, thereby giving the sensation of stretching. Do not buy a SIDI shoe in a size too small because you anticipate that it will stretch.