the shaft diameter is 20mm so thats the ID of the oil seal.
32mm is the OD and I used a 7mm depth...though I think an 8mm would be better looking at the pics. If you want to run a spacer like that as a dust shield. pick up the appropriate thickness)1.4-2.4) to make the overall depth the same(9.4xmm). your discretion if you want to do it.
If you can source the exact seal, let this post know!