Bolt Size?? Rear Malibu fiberglass bumpers

[classic_man]

Ok...so I am trying to figure out what size these bolts are. I'm putting on fiberglass bumpers. The rear bumpers fasten to the bolts that stick out of the rear quarter panel where the trim pieces used to be. I thought they were 1/4 in. but that is a bit too small and 5/16 is too big. Was hoping somebody would know of the top of their head. Thanks

 

[pontiacgp]

7 mm or if it's not metric 9/32

 

[classic_man]

Thanks! It was 7mm