Does anyone know of a reference for the different types/manufactures of A2 rear stocks?
I have a couple.........and would like to know which one would be best to use on my USGI M16A2 clone build.

One is grey and the other is black.  

The grey one has raised diamond patterns on both the butt plate and hinged trap door.
The black one has a smooth butt plate but the hinged trap door has raised diamonds.
Both are all plastic.

Thanks
 

As far as I know, there have been a couple versions. All plastic butt plate/ trap door, plastic butt plate/ alum trap door, and alum/alum assembly. But- disclaimer: I could be totally wrong. I heard the earliest A1/A2 plastic ones broke too easy. I'm not sure what kind of abuse it took to break one. Dropping your weapon, or butt stock to skull.