Profile: Heat Exchanger Products Corp manufactures the most reliable silicone tube plugs for several industries such as electrical generating plants both nuclear and fossil, pulp and paper and petro-chemical. Our brass tube plugs are made with a brass nut and bolt assembly. We manufacture the collar and washers from a non-water soluble hard plastic called hytrel and the silicone parts are of a vulcanized silicone rubber. These plugs are offered in either double size (two silicone parts) or a single size (one silicone part).