These are the original copper splice caps for the Buchanan C24 4-point crimp tool which I use for bonding ground conductors inside residential electrical boxes. Not cheap, but high quality and effective. These soft copper caps are listed for the 4-point crimper, where some of the other harder style "steel" caps are used for the single-point crimpers. There is also a larger copper splice cap to be used with the same C24 tool where more conductors need to be combined. Both are easy to use, allow multiple "original" ground wires to be used without having to add pigtails, plus they save space in crowded boxes.

Easy to use, very strong join

Whether it is in the current wiring codes of your community or not, it will be in the future. The NEC has specified that a wiring device cannot be a conductor.
That means, using the pushin holes for wires in the back of the receptacle can't be used. Using them means that if that receptacle is anything but the end of a string of receptacles, disconnecting it will remove all power to downstream receptacles or devices.

What is required now it a continuous conductor string for power flow. That is accomplished by joining the in and out wires together with jumper wires that connect to the receptacle. For hot and neutral, these crimp connectors do a far better job than wirenuts. When these are installed properly, the connection is visible before the cap goes on. With wirenuts, nobody is quite sure whether all the wires are firmly attached.

All the wires must be twisted before slipping on the copper connector, then a Buchanan C-24 Crimper MUST be used to crimp the wires together. Pliers or other crimpers will not work properly. The C-24 crimps from 4 directions compressing the wires and holding them in place. After the crimp, any excess wire protruding out the end needs to be cut off. Then the plastic cap is pushed over the connector. It locks in place. These connections cannot be undone. They must be cut off if there is ever a need to replace one.

The exception for including a receptacle as part of the conductor string is a GFI receptacle. For downstream receptacles tp be protected from ground faults they need to be wired through the first GFI receptacle. The problem with the cheap GFI receptacles is that they are unreliable. Cheap versions may not work at all. Plus some of them are made for 14AWG wire. 12AWG which should be used for receptacle wiring.

The advantage of using 12AWG for receptacle strings is that it can be protected by a 20 amp circuit breaker. The rule of thumb for the number of receptacles on a string is allowing 3.5 amps per receptacle. For 14AWG the limit is 4. For 12 AWG, it is 5 or 6. When using a GFI circuit breakers, which are very expensive, in the main panel, the difference in the numbers can save the price of another GFI CB.

The Buschanan C-24 crimper isn't sold at the big box stores even though they sell the crimp connectors. Authorized distributors sell them or they can be purchased on line at Amazon. They last forever.

I have used them in the past and worked as I expected.

Product great for what I ordered it for and to do. And plan on ordering another.