Sorry – this should have been on the post above but I accidentally closed the page.
Anyway….
"…. the Mite-E-Bites are new to me …"
Thank you for drawing our attention to them. I looked up their manufacturer's web-site, assuming we are looking at the same items by the same manufacturer, whose name is actually "Mitee-Bite".:
Mitee-Bite LLC – an American or Canadian company – calls them "Fixture Clamps" within a range of various patterns of work-holding clamps, and explains their principle, with an eccentric rather than standard screw, and an arrangement to prevent the hexagonal body revolving. They look expensive, but I would expect that as the entire range seems intended for jig-work for high-precision, high-volume production. So I would not be surprised they came with your CNC mill as O.E. attachments, but might not otherwise be readily available.
Or… "Mite-E-Bite"? Who has closely copied whom?