FEP is a form of Teflon. FEP stands for fluorinated ethylene propylene, a fluorinated hydrocarbon. It is the most common type of

Teflon and is often foamed in constructions to reduce its dielectric constant (and velocity of propagation).
Belden makes many products which use FEP. Virtually all of them are plenum versions of standard cables. The foamed FEP is either the

insulation around single wires (in twisted pairs) or the dielectric around the center conductor in coax cables.
FEP can be used where plenum ratings are required, better electrical properties are needed, or where size may be of concern.
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