Need help finding specs on hex bolt

I stole this picture from another thread because it was the best of what I'm writing about and couldn't find it anywhere. The hex bolt in this picture, mine wasn't tight enough and fell out after installing an AAL. Could someone point me in the right direction as far as size, or part number?

 

Any bolt that fits will work. Go to a hardware store.

 

Yeah but you have to make sure it's either Grade 8 (for American units) or metric grade 10.5 (what is used from factory)

 

Home depot sells some nice metric nuts and bolts that are grade 10.5 (IIRC). They are in drawers and are yellow zinc plated.

You can also check boltdepot.com as they have about every size imaginable and are very well priced.