Useful for cleaning out mud, dirt, and light obstacles from ducts before installation of cable | Can be used around tight bends due to convex contacts between disks | Tapered profile allows pulling in either direction with pulling eyes on both ends | Polyurethane disks do not damage inner walls of duct | For use in 3-1/2-Inch ductsAmazon.ca Product Description MANDREL-PLASTIC 3. 5" (39259) From the Manufacturer Greenlee flexible mandrels are useful for cleaning out mud, dirt, and light obstacles from ducts before installation of cable. Can be used around tight bends due to convex contacts between disks. Tapered profile allows pulling in either direction. Pulling eyes on both ends. Polyurethane disks do not damage inner walls of duct.