The connector barrels are made of monolithic copper, polyolefin tubing shrinkage ratio: 3:1, heat activated adhesive lining with insulation up to 8mm and inserted into the terminal barrel. Tighten the insulated connector for a solid connection and heat the tube evenly for about 20 seconds with a heat gun. Check your waterproof connection and allow it to cool before use. Tinned red copper, waterproof and waterless thermal connectors, operating temperature: -67 to 257F, minimum shrinkage temperature: 176F, full shrinkage temperature: 266F, waterproof and waterless thermal connectors. Operating temperature: -67 to 257F, minimum shrinkage temperature: 176F, full shrinkage temperature: 266F. Polyolefin heat shrink tubing.