I am assuming this is the speaker grille you bought, correct?This is what is shown in my pic.
Universal Platform Base with Dual 20mm Mounting Balls and MagSafe Phone Holder
I also have another arm and the clamp style phone holder from a previous vehicle.
66117AN02A - Speaker Cover - Genuine Subaru Part
Genuine Subaru Part # 66117AN02A - Speaker Cover. Fits Legacy, Outback