Stan, DO NOT do what Dylan told you,read below
Ok look, you do not have to cut anything in the rear to fit just chrome tips, u dont have to add a rear spoiler either. Yes the rear spoiler will look nice but u DO NOT need it. Now i know all this because I have a C240 and i went to 'www.performanceproducts.com' and they had a dual tip chrome exaught and there big and they go up in a 90 degree angle so they come straight out and dont til downwards. It look sooooo good. Hope this helps, i just didnt want to have you start cutting upart your car or spend another $500-1000 on a rear spolier you do not need