25028A: M18 - 4.1mm ring diameter, 1.0mm ring thickness.

25028B: M22 - 4.8mm ring diameter, 1.0mm ring thickness.
 

Stock Image.

25028C: M18 - 5.2mm ring diameter, 1.4mm ring thickness. Has some scratches on knurled section but screws in OK when I checked it.

25028C Sctraches on knurled section.

 

25028C