http://ecx.images-amazon.com/images/I/418qSAO05SL.jpg <— This is what I received.
https://www.inventables.com/technologies/flexible-coupler ← This is what I thought I was purchasing, and what I actually need. The one I received (the top one) simply does not grip the lead screw very well. I nearly bent an Allen wrench tightening it to where it would not come loose. Again, I already have 3 of the bad ones, and I just threw them away because they were ruining work; I really did not want to spend a week waiting on another set of what I just threw out.