Siren Nuts are Mechanical collectibles in Xenoblade Chronicles 2. They can be obtained through Salvaging at Goetuis Wharf #1 Salvage Point in the Indoline Praetorium, or from the Salvage Points on Godsford Isle, Daram Isle and Ansel Hatchery in the Leftherian Archipelago.
Two of them are required to refine the Aux Core Fast Blade Switch IV.