Hi Mark. Just bought a new
hoyt epik riser and they put a few spare shims in so i could measure them for you. They have large and small shims. Large shims = Ext. Diameter 16.04mm (0.631 inch), Int. Diameter 13.00mm (0.511 inch), Thickness 0.13mm (0.005 inch).
Small shims = Ext. Diameter 9.52mm (0.375 inch), Int. Diameter 6.5mm (0.256 inch), thickness 0.13mm.
Haven't got clue where you can get them. Have you looked at the
hoyt Website?
Regards, John.