My K2 "Alexis" inline skates came with a brake pad bolted on to the shaft of the rear skate on the right foot. After a fall where my ribs were severely bruised by the brake shoved in to my back, I decided I'd be better off without it. So I unbolted the rear wheel and took it off, but the axel shaft is too long and was left loose without the brake attached. These spacers help make sure the skate frame grips the bearings properly and their taper helps keep the bolt heads from catching on anything. Made with Oozby - my OpenSCAD preprocessor, makes neat use of corner_radius option on cylinder() for nicer aesthetics.Print off two. I printed mine in generic black PLA using 20 shells (effectively making the whole thing out of solid shells). Because these need to be under a bit of pressure from the bolts, I recommend printing them solid or close to it. I don't think you need to fuss over materials too much with this. If they break the skates still work and are safe - they're just a tad more likely to catch on something and trip you up. Still I think it's a good idea to print it solid, with heaps of shells. Nice strong spirals.