These are speaker grills for a nice looking radiobox. I made it out of a small ammunition container.
I included the internal electronics mounting plate. On this plate you have various possibilities to screw or ziptie parts.
The four screw holes match this amplifier: http://dx.com/p/y148-audio-amplifier-module-93121
There are also possibilities to insert rocker switches.
The mounting plate features some groves which make sure the part doesn't warp.