Have added them to my business contacts.
I've only been using them for a couple of weeks but the fit is good and they are as good as OEM.
4 Inch caster. Fits Viper Fang 20HD, Fang 24T/26T/28T (replaces VF83111)
Fits Nilfisk Advance VF83111-1 (alt # vf831111)This part is listed as fitting the following models: