This is a parametric printable bearing with a two-piece hub that allows the tension on the balls to be adjusted. Tightening nuts against the hub pushes the balls against the outer ring to adjust for printer tolerances and so that it won't become wobbly once its worn in. The two-piece hub also makes it easier to assemble.
The script includes variables for inner diameter, outer diameter, bearing width, ball diameter, and the angle of contact between the balls and the hub/ring. It is designed to be used with vitamin bbs or round beads. All of the pictures are sized to match a 608 bearing (7mm width, 22mm diameter). The bearings are, from left to right, 6mm plastic airsoft bbs with a 3mm shaft, 4.5mm metal bbs with a 6mm shaftt, 4.5mm metal bbs with an 8mm shaft, and 3mm spherical beads with an 8mm shaft.