The GMP Tools Duct Seal, 10mm (P/N 89909, Millennium part 526773), seats in a GMP cable blower insert to seal around 10 mm duct so air pressure holds during a jetting run instead of bleeding off around the cable. Crews change seals like this to match the duct size on hand, letting one blower service microduct as small as 10 mm. Maintaining seal integrity directly determines how far cable can be blown in a single pass. Order it with matching duct clamp and seal kits for the rest of a blower's duct size range.