BuyHeatShrink 4:1 PTFE Heat Shrink Tubing - PTFE heat shrink tubing has a very high continuous use temperature (260°C), and outstanding chemical resistance. It is available in 2:1 and 4:1 shrink ratios, and meets or exceed the most stringent commercial (UL VW-1, UL 910, NFPA262) and military standards (AMS-DTL-23053/12). While it is the best of the entire fluoropolymer heat shrink tubing family, PTFE is also the most difficult to shrink due to its extremely high shrinking temperature (325-340°C). A heat gun or a welding torch can be used, but it is not recommended due to the tendency for the material to have localized over-heating or under-heating. It is extremely important when shrinking PTFE that the material is uniformly heated to provide even shrinking. We recommend you use a controlled temperature oven; although this is obviously impractical for large harnesses or areas adjacent to temperature sensitive components.