It looks like EZ Red designed their butterfly sockets for fasteners on which you’d normally use a flare wrench but can’t get the wrench around the fastener. Just wrap the butterfly socket around the fastener and when you close it, stick a 1/2″ ratchet or breaker bar into the square drive hole to turn it.
The shape of the sockets suggests they put the force on the flats on the fastener rather than the corners, so they’ll work with damaged or worn nuts. EZ Red even claims you can use the sockets for either metric or SAE applications.
Their small set includes 7/16”, 1/2”, 9/16”, and 5/8” sockets. Their medium set includes 11/16”, 3/4″, 13/16”-7/8”, and 15/16” sockets. Finally their large set includes only three sockets:1-1/16”, 1-1/8”, and 1-1/4”. Supposedly each socket can also be used on the closest metric equivalent size.
Look to pay anywhere between $60 and $90, depending on which set you get, where you buy it, shipping charges, and taxes if applicable.