Graphtex Ultra (GTU) is a blend of ultra-slippery W. L. Gore fibers and graphite braided fibers, impregnated with Teflon to produce a packing that will give the ultimate level of performance. This packing has a high thermal conductivity, providing superior heat dissipation and cooler shaft temperatures. Made of a synthetic fiber, it doesn't degrade over time, and remains soft, pliable and dimensionally stable throughout its life. Perfect for modern, high RPM applications. Rated to 536F; rotation speed of 4,400 ft/min Color is black