A1 Mini mod to reduce the likelihood of filament tangle on the reel when the print head moves from the top to the base of the heat bed. It allows the filament to remain stationary on the reel when the print head moves rapidly up and down. I've had it get twisted on the reel spool in some cases but this reduces the likelihood of this happening.
A video showing it in operation is at https://youtu.be/Xd_1KKXulAI