I'm mostly ambivalent on these, would like to never have to use one, but perhaps 2 interesting points. (1) Unlike most components used in wiring a building with NM, where all those cc components are rated/tested for 600 volts, I have read to the test for these is 300 volts. (2) On the committee vote, the one negative ballot is the IBEW representative. That is interesting both ways - pro-labor or knows what happens in the field.
I'll guess there are a lot of jurisdictions that will amend these out.
Having trouble finding on on internet. Found 1 - $13.00 +s&h I think a box, cover, 2 screw connectors, and wire nuts cost a lot less.