19.1mm ~ 0.751" You dont need the bearings with cages. It just helps in assembly. Measure one of the balls dia and see if you can find loose balls at a bearing distb/bike shop. Put some heavy grease in the bearing cup (the cup is in the piece that comes off) and start placing as many balls in as you can, usually 2 or 3 more than the cage bearing. The heavy grease will hold them in place. Carefully assemble. This is how big dollar bicycles where in the 70s/80s (Campagnola parts). More balls, allows more load, and while you're there check the other bearing. Don't forget to check for end play.