EFFECTIVE_ON is the name of the set. Here's the set for refference.
private static Set<Block> EFFECTIVE_ON = Sets.newHashSet(BlockInit.AMBER_BLOCK.get());
I could ofcourse replace EFFECTIVE_ON with the set but I would then have to repeat this for each item it is applicable to.
It is used when creating a ToolItem in the third argument.
public static final RegistryObject<Item> IRON_GEO_HAMMER = ITEMS.register("iron_geo_hammer",
() -> new ToolItem(1, 1, ItemTier.IRON, EFFECTIVE_ON, new Item.Properties()));
Do I need to change anything here?