Front Shock Absorber For Mercedes Benz W221 Our Mercedes W221 front air suspension shock absorber (part number 2213204913) is a premium aftermarket air strut designed to replace the failed original air suspension unit. Air suspension failure is common on Mercedes W221 models due to aging air springs, which leads to vehicle sagging, abnormal noise and poor handling. Our replacement air shock effectively solves these problems. Every air suspension strut goes through air