This was news to me, and I have worked with these cans since their introduction in the mid 80s.
Here is a link to scepter's parts pages. For those who still work within the military system, not all of these parts are catalogued into the Cdn NSN system, and some of those that are end up being local purchase.
https://mil.sceptermilitary.com/fuel...acement_parts/
One neat thing about it is that it explains all the colour codes of the rings. There are a couple of odd ones like mixed fuel, waste, and kerosene.