This is the FLD bezel used to center the lights and make sure they look right inside of R2. When making the lights, this goes over the LED before they are soldered to the PCB. This is important to ensure they look good.
Researching the lights
Researching the lights can be confusing at times especially when learning the names and what they do. Once you have that figured out, you need to research how to build them and that is when things get a bit scary, especially if you are electronically illiterate. Don’t let it scare you! Once you get pointed in the right direction, it gets easier. A good place to start is the Droid Wiki parts terminology page.