Erlenmeyer Flask, Teflon found in: Teflon FEP Graduated Erlenmeyer Flasks With Screw Caps, Corning Media Storage Caps, Filter Degasser, Combine the near.. Combine the near-indestructibility of Teflon® FEP with the convenience of a screw closure Unbreakable, nearly transparent, non-contaminating, and resists virtually all chemicals Flasks withstand temperatures from -270 to +205 C; closures