Yeah, they worked great. On my Idrive build I used a controller and harness from another bike and the wires were a little short to reach my seat bag. I got them in thru a little hole I punched in the bag, but they weren't long enough to come out the zippered end, so I had a prob. soldering all the wires to the controller wires, so I just used sm. wire nuts. W/ these butt connectors, I was able to solder them together Inside the bag! As long as one wire has at least an inch exposed(the butt connectors can be trimmed), just slide the sleeve on and twist the wires together and slide to sleeve back over til the solder band is over the twist joint and focus a pin-point flame on the solder band. The sleeve is clear and it's easy to know when you are melting the solder w/out melting the shrink-fit. It makes a three-handed job(holding the iron in one hand, the solder in the other and somehow trying to keep the work steady) into a two-handed job(holding the torch and slowly rotating the work).
Every ebike tool kit should have an assortment of these.
https://www.gearbest.com/diy-parts-components/pp_009668199398.html?lkid=15477277