If you need locking nuts that go on and off easily and if you are working upside down - like on a fuel pump assembly - these will put a smile on your face. Having the shoulder on the nut keeps them at the top of the socket and not having to put on a separate locking washer that keeps falling off will save you time and frustration. They are even gold zink plated so they are a close match to the originals.
The locking feature is built right into the nut so there is no need for a separate locking washer.
Here is what they look like on the fuel pump shock mounts common on soooo many models!