Rear Speaker bolt size?

[bcrooms]

Does anyone know the correct size of the factory rear speaker bolts?  I have replaced my factory speakers with aftermarket speakers that required an adapter for proper fit, and the adapter obviously has added material between the bolt washer and the body panel.  The factory bolts are too short to use with the aftermarket speaker + adapter. I tried using the screws and such included with the new speakers but those screws aren't the right size for the factory holes....

 

I've checked a few hardware stores in my area but I can't find anything that is close to the factory bolts.  I just need the same type but slightly longer.

[richard wysong]

They are probably metric, most hardware stores have a device to determine the size and pitch if you ask