This document discusses the main types of raw materials used for screen protectors - PET, TPU, and glass. It focuses on explaining the different types of glass, including German Schott glass, American Gorilla Glass, Japanese Asahi Glass, and various Chinese glasses. It provides advice on how to identify the raw material quality, such as by observing the glass sheets and testing sample breakage. The document emphasizes the importance of choosing reputable suppliers that use higher quality materials like Asahi glass if targeting markets like the US, in order to protect your business and ensure customer satisfaction.