This is the distinctive steel cup, which is pressed into the end of both front and rear Norton hubs on the brake side, and retains the felt washer, to stop grease escaping into the brake drum. This version is identical to the original Norton version (one of which was used as the template for these), and is useful, as originals often get bent and distorted as part of fitting new wheel bearings
As I am sure many of you have found - even if you have one of these available on your own hub, chances are it will be in bad condition if it has previously been prized out and punched back in, when the wheel bearings were last changed.
This pressed cup is high quality and identical to the Norton original that was used as the pattern. To fit, place it above the recess on the brake side of the hub, then use a small punch (or screwdriver) to push it into the recess. If your hub recess is worn, you can also put a couple of additional punch marks on the rim of the hub, as per the plunger hub shown here in the second photograph