This 3D printed plastic frame reduces backlight bleed in Game Boy consoles that have been modded with the IPS display. This display naturally cause some light to bleed around the edges. This protector sits between the LCD and the lens to minimize the amount of light visible at the sides of the screen.
Didn't get rid of all the light bleed I was expecting more but it does help maybe some soft material as a gasket that sticks to both sides that squish between from and back of the 3d printed piece may help