These are the best and easiest-to-use butt connectors we can find. These splices have solder already enclosed and an adhesive-lined insulation that melts when heat is applied.
The soldered connection provides optimum conductivity, and the adhesive-lined heat-shrink insulator provides excellent weather resistance and anti-corrosion properties.
Just strip the insulation off your wire ends, crimp in place, then heat to melt solder and seal the connector. Done!