ION virtue, vlocity loader, smartparts barrel, and lots of little things...
It doesnt affect your game much its just cool looking.
Kinda expensive but it looks amazing when you get it on there, i would still say it is worth it. I bought it a while ago and put it on and i was amazed right away.
I told my friend to buy it he did he got the blue (i have red) i thought the red would look the best but when i saw the blue it looked just as good. I have not seen the green with my own eyes but both the red and blue will make your marker look a thousand times better.