The Hexatronic Cleaning Sponge (NTM50207/3, Millennium part 522849) is sized for 10-15 mm ID microduct and gets pulled or blown through the duct ahead of a fiber jetting run to clear out dirt, moisture and debris that can slow a blow or damage cable jacket. Sold in packs of 100, it gives crews enough stock to proof multiple duct runs across a job. Cable placing crews typically run one through fresh or reused duct as a standard pre-blow step. Stock it alongside duct proofing kits and matching cleaning sponges for other duct sizes.