The original of this item was for bottom feeding filament but I recently moved my spools above my printer so I needed a top down approach.
Print both halves, break out the half circle, then glue together and stuff a sponge inside and put your filament through it for great filament guiding dust and clog free printing. I've been using a variation of this for over a year and have never had a serious clog yet.
Just added a new version that should fit on both the left and right edges of a Thing-O-Matic.
Also, I'm aware that "left" and "right" are reversed. It's a remnant from original thing I derived this from. Print one of each and glue them together and you'll be fine.