Flexible foam body for an air-tight seal | Color-coded end disk with embossed size markings for fast, easy selection | Strong steel center rod with loops on both ends | Pistons available for all types and sizes of conduit 1/2" through 6"Amazon.ca Product Description Greenlee's conduit piston is for use with blower or vacuum power fishing system to pioneer the line through the conduit run. From the Manufacturer Greenlee's conduit piston is for use with blower or vacuum power fishing system to pioneer the line through the conduit run.