You need one 607 ball bearing. I recommend a ceramics bearing since this things spin forever (C607). The other three bearings are just to add weight. These can be normal 607 bearings. The "ZZ" variant looks nicer since it has fully enclosed sides. Here is the ceramics ball bearing I used (open type): https://www.kugellager-express.de/keramik-hybrid-miniatur-kugellager-c-607-7x19x6-mm.html No special slicing instructions. You could slice at 0.2mm layer height and 30% infill. I went with 0.1mm layer height and concentric infill (latest Cura). For the dual version I changed the "dual overlap to 0.2mm".