FITS THE FOLLOWING 201 chassis 124 chassis ( 1986 - 1990 300E , 260E , 300CE and 300TE ). If you are experiencing rough idle, poor throttle response, or your gas mileage has gone down recently, it is probably time to replace your oxygen sensor (it is located under the car on top the forward section of your exhaust system). As these cars are now getting 12 - 15 years old this is one of those things that wears out and often does not get replaced. New factory one is over $150 from your friendly dealer. I have discovered Bosch makes the identical sensor and markets it as a Universal three wire for 1/3 the price! This means you will have to cut the wires and splice on your factory plug but I think it is worth it, don't you? INCLUDES ILLUSTRATED INSTRUCTIONS.