This is a replacement barrel nut for Wooden Clip. This is the metal tube that is inserting in the wooden clip which the plastic screw screws into.
There are two versions of these barrel nuts. In the drop-down menu choose the color of the metal screw visible from the top of your wooden clips (silver or gold) to select the correct version of the white plastic screws for your loom. If you are purchasing a loom today, choose GOLD.