I was tired of having overly long spool hangers sticking off the side of my printer and having to swap them out when the hub of the spool needed a different size. I decided that the spool only needs support on one side and set off to design this holder. Since my printer is built using Misumi 20x20 extruded aluminum, I decided to take advantage of it and utilize it to provide a linear slot. This slot allows the pieces to be fully constrained and by loosening the bolt it has 1 degree of freedom. Very handy indeed! You place the spool in the lower portion, loosen the bolt for the upper piece, then lower it down to capture the spool on the top edge, then retighten the bolt. At this point, the spool is fully captured and cannot fall out, yet is able to move freely in the holder. As you can see from the photos, this works on a variety of sizes of spools with a simple vertical adjustment of the top piece. I prefer to have some friction to prevent the filament from spinning loose on the spool. With no modifications and printed with PLA, this holder has low friction, allowing smooth operation with no binding or loose coils of filament. If you prefer less friction, you can smooth the contact surfaces or even add some teflon tape to them to reduce friction. If there is sufficient interest, I will design a version with bearings for all the freewheeling, filament tangling fun you desire. This was designed on "ON Shape" web based CAD. Here is a link to the project. https://cad.onshape.com/documents/6aa32e19c828316ad3dc0215/w/7ecae9aaefe9057e79e0a774/e/21d6c2c45bed128a63d94fd8 I think there will be more revisions to come, but I need to test it for awhile to find the weak points in the design. Having said that, it works quite well as-is and have had no problems with it to this point.