PETG (Polyethylene terephthalate – glycol modified), is the result of a modified PET filament that is clearer, less brittle, and easier to use than the base form of PET. It is more durable. Overheating regular PET makes it hazy and brittle, but not with PETG filament. The added glycol prevents the material from crystallizing and becoming breakable. It is highly impact-resistant. Unlike PET, it is RF sealable.