The tiny metal tube insert on these connectors is very thin; doesn't warp like the famous branded parts I've used for years. Decided to try these but won't be returning. They flex when crimped but do not effectively wrap around the wire, forming a strong, electrically secure connection. Despite repeated crimping and vigorous turning of the handles, some fittings came loose easily. It may not be safe to use the port. I take them out of my tool box and throw them away. Don't be shy to spend more for connectors that work the first time.