Fixed jet--don't like them .The Mac 105 I have had one which I replaced with a fully adjustable from a 125 .As I understand it they used the fixed jets to cut down on warrantee work caused by people running them too lean.Most reeders need to run just a tad on the rich side to get the most out of them .The fixed jets had the main jets sized for the altitude where the saw was sold at.That said a fixed jet won't hurt them .
I'm not sure what I did with that fixed jet but I think I hung it on a 7-10 .However it could be in one of the coffee cans full of carbs hiding in my garage.Damned cans are elusive,they hide very well