Cleaned and certified to CGA G-4.1 - (maximum contamination level of 47.5 mg/ft2 for use in oxygen), this 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. It has an operating temperature range of -450ºF to +500ºF, contains no contaminants, and is highly resistant to chemical attack.