If you mean the Red outlined part then its just a chrome cover covering the muffler headers. If you mean the green outlined part then they are more muffler covers but are not chrome but you can get them chromed.
But, then if you mean the tubular bar that is in front and under the engine then they are engine guards and come in very handy when the bike falls over. (Don't ask me how I know)
If it's something else then you will have to show a picture cause I have no idea what else you might mean.