Review on Qibaok Waterproof Electrical Connectors - Automotive & Industrial Applications by Marcus Braunstein

As with many of these cheap crimp connector sets, the center crimp sleeve is machined from the cheapest Chinese metal. It will crimp, but it's too soft to hold the wire securely. Don't use them for anything critical, especially on smaller wires. I think the larger sizes are better (maybe more metal) but the small ones (which are most in this set) are almost useless. Heat shrinkable exterior 3:1 no epoxy filled with marine material. , so it offers only a minimal level of water resistance. It also doesn't hold up very well to the crimping process, meaning you'll pierce (or at least distort) it as you crimp. Low quality, low reliability. Buy something else when you're doing important things.