GMP Tools part 34267 is a 6 mm stainless steel cable blower insert for small-diameter microduct work. Stainless construction resists corrosion from moisture and duct lubricant, so the insert holds its dimensions and sealing surface through repeated wet-weather deployments. At 6 mm the tolerance matters: the correct insert keeps air pressure behind the fiber instead of bleeding past it, which is what determines usable blow distance. A standard spare for crews running micro fiber blowing equipment on FTTH routes. Stocked by Millennium as part #543943.