Review on 🔌 Kalevel 120pcs Breadboard Jumper Wires Kit - Male to Female, Male to Male, Female to Female Jumper Wires - Long 20cm Ribbon Cable (M-M, F-F, M-F) by Ricardo Ware

I bought a bunch of these a few years ago and whenever I've used them as jumpers they've been ok. A few days ago when I cut the wires and tried to solder the cut end to the board I found that the wire was aluminum with a very thin copper coating. I looked at it under the microscope. The copper plating is oxidized and dark in color. When I peel off the oxidized coating, shiny aluminum is revealed underneath. It is impossible to solder this material and get a good connection. I'll see if I can find some that use real copper wire.