Top mount filament spool holder, designed for 2020 T-slot. It is vaguely similar to the Prusa MK4S filament holder but also to a many other different models I saw online (but there really is not just one I designed it from). Basically I wanted to be able to hold 2 spools parallel to the top bar and for it to secure to a common 2020 T slot. I designed the shape it so that it could be printed without supports. I designed the handle in two pieces so that it can be printed flat for strength without using supports. To keep the handle together I printed an end cap which is slid over the two handle parts (on purpose it is a tight fit, but you may need to make small adjustments depending on the tolerances of your printer) which also serves to keep the spool of filament from falling off. The other end of the handle is secured by simply screwing it in.  You will need 4 T slot nuts (I used size 5 on mine) and bolts to secure it to the  2020 T slot rail. I use it on my Longer LK5Pro.

It works well when printed in PETG although I am certain other filaments would also work well.

I also designed a filament guide (which you can see in one of the pictures) based off the guide on my MK4S which I will list separately (since that design is a remix of the MK4S filament guide and thus will be credited appropriately as a remix)

https://www.printables.com/model/1384090-filament-guide-for-top-mount-filament-holder