A method for coupling ends of two insulated conductors includes coupling an end portion of a core of a first insulated conductor to an end portion of a core of a second insulated conductor. At least a part of the end portions of the cores are at least partially exposed. Electrically insulating material is placed over the exposed portions of the cores. A sleeve is placed over end portions of the two insulated conductors to be coupled. The sleeve includes one or more raised portions. The end portions include the exposed portions of the cores. The sleeve is coupled to jackets of the insulated conductors. The raised portions of the sleeve are mechanically compressed until the raised portions of the sleeve have a diameter substantially similar to a remainder of the sleeve. The compression of the raised portions of the sleeve compacts the electrically insulating material inside the sleeve.