Dura-Line Smooth Wall (Smooth Out / Ribbed In) HDPE conduit/innerduct — flexible HDPE conduit for underground and inside-duct installation. Product family meets or exceeds multiple industry standards (ASTM F-2160, ASTM D-3350, ASTM D-3485, NEMA TC-7, UL 651A/UL 1990, Bellcore GR-356) and is available in sizes from 1/2" to 6" with multiple SDR/SCH wall types (including SCH 80). Offered in multiple colors and optional striping; options for factory-installed pull tape (including none) and a range of reel/roll lengths depending on size. Source data compiled from Dura-Line product pages and datasheets plus distributor product pages (Chapman Electric, USA Supply, Graybar, Mountainland).