A very simple upgrade for the SeemeCnc H1 printer is replacing the idlers for the belts with ball bearings. Using the stock bolts this means we need a sleeve to go from the 1/4" cap screw to the 8mm ID of the bearing.The bearings are cheap readily available skateboard bearings. Also known as 608 size. Measurements: 22mm OD 8mm ID 7mm heightThis is quite possibly the second simplest STL on thingiverse after a cal cube!The only important thing to do is make sure it prints as just perimeters/shells, infill isn't really the way to go on something so thin.My printer had alot of backlash (therefore the part wasn't as round as intended) so I had to run a 5mm drill through after printing.Works great, print a couple at a time (I did 4) so each layer has time to cool.The 'stack' when assembled should be: Cap screw1/4"ID x 1-1/16"OD x 1/16"Thick Plastic Washeridler_sleeve + skateboard bearing1/4"ID x 1-1/16"OD x 1/16"Thick Plastic Washer Z axis plate10-32 Nylon Lock Nut Stainless Steel