So I was rebuilding a carb this morning and I got to wondering. What the heck are these little metal ovals they send with the carb kits? I've seen where they go in the carb itself but what are they for? I have tried once to pop the old ones out but they are really stuck in there and look like you need to press em in maybe with a special tool or something. Saws run fine with just a regular rebuild without replacing these. So does anyone replace these when they rebuild their carbs?