Some people who are new to the world of gun holsters mistake Kydex for a brand of holsters. In reality, Kydex is a specific brand of thermoplastics that has also become a generic term for polymers in general. In other words, Kydex is a material, like leather or nylon.  Kydex brand thermoplastics are very high-quality, but so are most thermoplastics used by reputable holster manufacturers, like the ones recommended here.