PETG (PolyEthylene Terephthalate) has become well known from plastic bottles. In its original state PET filament is a colorless and crystal clear material. But when you heat or cool down the material changes its transparency.

The material has more crystalline structure when allowed to cool down slowly after printing. The filament is fairly hard and shockproof, so it makes it ideal for lightweight items. There are different versions of PET, and PETG is the modification of the one, that is clear thermoplastic with possibility to thermoform and mold the item after being printed.

It is also possible to polish the material with flame. Also the thicker layer height the better clarity would have the material. Generally PETG is nice and easy material to print with quite wide temperature range from 160°C to 210°C without any problems. But it needs to be stored in a place where it would not absorb water from air.