HK Series Industrial Interchange Series B Dust Cap, -12 Coupling

Buna-N comes standard and handles a range from -40F up to 250F, so it holds up fine in cold conditions most folks run into. If your setup gets colder than that or runs hotter than 250F, there are other seal materials available including Neoprene, PTFE, FKM, EPDM, and Kalrez. EPDM and Neoprene both go down to -65F on the cold end, with EPDM reaching up to 300F on the high side. FKM tops out at 400F if you're running in a real hot environment but its lower limit is only -15F so it ain't the pick for cold-weather work.