From Fobus Website..."Fobus is the first manufacturer of injection molded polymer holsters , with this experience Fobus is the leader in high-density space age polymer."
From the Wikipedia definition..."KYDEX is a line of thermoplastic acrylic-polyvinyl chloride alloy sheet grades. It is frequently used as an alternative to leather in the production of firearm holsters and sheaths for knives. KYDEX® Thermoplastic Sheet is a registered trademark of KYDEX, LLC and is the only manufacturer of this material." "The combination of strength properties of KYDEX® sheet places it at the highest level among thermoforming materials. Its modulus of elasticity in flexure is 330,000 psi - 50% higher than many other sheets." "KYDEX® sheet is a relatively hard thermoplastic with a hardness of 90 on the Rockwell R scale. In service, this excellent abrasion resistance is further enhanced by the grained surface of the Kydex sheets."
The Fobus is a polymer...no doubt. It is however NOT kydex. There are some very fundamental differences in both the chemical composition and overall feel of them both. The Fobus is a polymer that is injected in to a mold like Jello or cupcakes and sets up to form the holster body. Kydex comes in various thicknesses in sheets, and is formed by hand or with tools and heat.
A lot of people dont know the difference. The Fobus is a very serviceable holster for a lot of people and their application. I personally dont like them but to each their own.