This is the easiest way to make soldered splice in your wiring. It is our favorite way to extend the wires on stepper motors.
This part combines a low temperature solder ring inside a piece of clear heat shrink tubing. It also has rings of hot melt glue at each end. You strip each wire, insert one from each end and cross the stripped ends inside the solder ring. You then heat the tubing with a heat gun. The solder and glue melts and the tubing shrinks. You get a reliable, insulated, waterproof and soldered connection in one operation.
It is also great when you need to fan out one wire to several wires. This often happens when you have one ground terminal, but four wires coming to it. Place the four wires in one end and one in the other end.