Love my DF54, but the bellows had a flaw. The rubber, at rest, was the exact size of the aluminum ring it mounted on, which meant that it never stayed on. A quick hack of a rubber band on the grinder itself took up the space and mostly worked, but I never could get one just the right height and the bellows would come off ever so often. So, I 3D printed this.

It's a simple split ring. The ID is 55 mm, OD is 57mm and it's 4.6 mm tall (OD and ID are intentionally slightly over- and under-sized). The gap there is an arbitrary 5mm. Printed in PLA. Put it on the grinder, stretch the bellows over it and now the rubber is actually clamping on something. Super simple and it's now been solid for a few weeks of use.