My 135 has a different front sight with a hood and no set screw. Looks like yours has a set screw. Just take the set screw out, heat it with a hair dryer for about 30 min. and you can twist it off easily. Do you know why it looks like it turned gray
Go to Pyramyd Air. In the search window type muzzle break. You'll see an Air Venturi muzzle break, .655/.590 ID, .855 OD. $25.99. Part# SKU PY-A-4753.It fit my 135 perfect without the inside adapter. It's for looks,not very heavy.