Teflons can be chemically treated to allow etching or they can be composed of several additives such as glass, glass fiber (fiberglass), graphite, bronze and many others. The available teflon grade are PTFE, FEP, MFA, PFA, PVDF, ETFE, ECTFE, PCTFE and PVF. Please, note that for PVDF, "tube" and "roll" formats must be specially ordered.