I have been a loyal customer of Monoprice for almost ten years, and have been impressed with the quality of goods available. However, these twist connectors didn't fare as well for me. The screw lugs that are used to attach the wire to the connector were cross-threaded into the lug on 1/3 of the terminals, and made some of them impossible to tighten without ruining the tensioning screw. On most I had to remove the screw and attempt to thread the screw properly, but some of them wouldn't work. I ended up just tightening them to death to make the connection, and now I have ordered twist connectors from another vendor to replace all the units I ordered. Also, the twist lock part of the connector wouldn't lock into place. Without pressing on the unlock lever, you can remove these from the amp or speaker by just twisting them.
I used these to make my own NL4 to 1/4" cable because my power amp has NL4 connectors and my unpowered speakers are 1/4" jacks. Monoprice dose not offer this design yet but that would be a great ideal as many power amps are using NL4 connectors more often.