Chemistry - What are the plastic connectors called (for glassware)?

Solution 1:

Those are called Keck Clips. 24/40 is the size of the joint.

Solution 2:

They are called Keck clamps.

Here's a link to the page for ChemGlass:

Solution 3:

The clips are named after Hermann Keck - Chemistry World's Classic Kit columnist, Andrea Sella, spoke to him to get the story of the invention before he died a few years ago.