The batch I had made were:
11.45 mm internal bore throughout
Base section 19 mm outside diameter, 4.7 mm height
Upper section 14.21 mm outside diameter, 5.2mm height above base.
For me the crucial dimension was the height of the upper, thinner section. My new Titon belts had thicker plates than the originals and I needed taller spacers to allow them to swivel.
5/16" = 7.94 mm
7/16" = 11.11 mm
Jonathan