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. Kent especially likeqs to use these in behind the door panels when removing them for service. Many times the original nuts for the window regulators and the door check straps will loosen up. He just replaces all the nuts with these instead. The shoulder of the nut spreads the load out over the sheet metal to help prevent cracking and the "teeth" will keep the nut from loosening up in the future. They also work great to mount fuel pump assemblies under the rear of the gasoline models as previously noted.
The locking feature is built right into the nut so there is no need for a separate locking washer.