Ender 3 Filament Guide Cap

I've been using TheViralDIY's Screwless Filament Guide, and those deep-groove pulleys have done a great job keeping the filament in check. That is, until I ran into The Evil Spool. I don't know if the filament was stiffer or if the spool center was out of round so it rolled funny or what the cause may have been, but that sucker would throw the filament out of the guide as soon as your back was turned. So I fabbed up a slip-on cap for the filament guide, and no more Evil Spool.