Expanded PTFE Valve Stem Packing is an all purpose, self-forming packing material made of 100% PTFE.  It is a round, expanded product, resulting in a fibrillated, High Tensile Strength material that deforms when compressed to fill all surface irregularities.  PTFE Stem Packing is self-lubricating, eliminating stem wear, and is unaffected by most common chemicals