Style 691 is a braided expanded flexible graphite yarn reinforced with an Inconel wire jacket knitted around each yarn. It also has a sacrificial corrosion inhibitor.

Style 691 is available in the following cross-section range:
1/8" to 1 1/2" (3.0 mm to 38.1 mm)

Applications
Style 691 is recommended for steam, water, oil, solvents, alkalis, acids, and most chemicals. Exceptions are oleum, fuming nitric acid, aqua regia, and fluorine.
Style 691 is typically used for high temperature valve and other static applications, as well as some rotary applications such as soot blowers or rod packings.