Panduit NNC37X37LG2 Type NNC Halogen-Free Metric Wiring Duct, PVC, 37 mm x 37 mm x 2 m, Light Gray (Pack of 20). Slotted Duct, Halogen Free, 37 mm x 37 mm x 2 Meters, Light Gray, Made of halogen-free modified polyphenylene oxide (mPPO) material and verified with IEC 60754-2 test method (test on gases evolved during combustion of electric cabling).