A/M stands for After Market which are imitation parts shipped in from overseas.
The problem with A/M parts is that they are often poorly fitting and have never been crash-tested. There is not one automaker that stands behind aftermarket parts usage in the repair of their vehicles. So why should you?
Not only that, in some cases it can even void your warranty or cause you to pay out of pocket if the vehicle is a lease.
If you see A/M suspension parts you should run for the hills! Who benefits from putting aftermarket parts on your car?