About Polyester|Polyester thermoplastic (PET or PBT). Good mechanical properties, dimensional stability, and chemical resistance. Used for electrical connectors, structural components, and food processing equipment. Machines well with standard tooling. Compare to Acetal (better wear resistance) and Nylon (tougher but absorbs moisture).
About Sheet|Thin flat stock, generally under 3/16", used for stamping, bending, shearing, and laser/plasma cutting. It's the starting material for enclosures, panels, brackets, and formed sheet metal parts.