T-galse, short for Tough Glass, this new and unique filament has some very interesting characteristics with regars to clearness and strength. It is made from the highest optical quality PETG material. Unlike other polymers, some PETG, including T-glase are not considered "transparent". Instead, it belongs to a group of polymers that are considered "colorless" and or "colorless with a percentage of reflectivity".T-glase is also considered "water-clrar" and "optically correct".