Review on 💧 Waterproof Automotive Electrical Connectors by XUUAP: Ensure Reliable and Durable Connections by Brandon Daughenbaugh

They take a little getting used to so some practice is needed before you can actually splice. The outer plastic becomes VERY SOFT at the temperature required to melt the solder so care must be taken. If you heat the plastic a little, it will char. Once you get used to them, they will work very well. It is highly recommended to use a heat gun instead of matches or lighters. A small hand-held heat gun will work with the smallest (white) fittings, but for the next size (blue) and larger you'll likely need a full-size heat gun.