Inside the Shroud: Thirteenth Eclipse raid, you get three sizes of ingredients to upgrade green steel items. Each level upgrade requires 12 ingredients of the matching size.
Within the raid, there is 1 chest dropping small, 3 chests dropping medium, and 2 chests dropping large. (However, you typically only go up until the first large chest).
I can understand why the devs would want large ingredients to be rarer than medium; better stuff is usually harder to get. But I don't understand why small is three times rarer than medium...
Phase 1: Small
Phase 2: Medium
Phase 3: Medium, Medium
Phase 4: Large
Phase 5: Large
It might be good to if there were some way a player could use larger ingredients in a smaller recipe, such as a certain collector NPC who will exchange med items for small ones (of the same kind).