I was skeptical at first but I thought what the hell I'll give him a try. I needed to rewire a engine wiring harness. I thought that these may save me some time and they definitely did. HERE'S MY 2 CENTS. Slide one of the wires in half way, the heat that end so the heat shrink tube closes but make sure you don't active the solder. Now that end and wire is held in place. All you need to do is put in the other wire and finish. Super easy.