This is an OEM left front axle-shaft manufactured by GKN - the original supplier to BMW for this part. As the OEM it meets all of BMW's original design, fitment, and performance requirements and is TUV approved. OEM parts are the best alternative to more expensive Original BMW parts because they are virtually identical without the inflated price tag. This part has a two year warranty.
Axle-shafts, often called half-shafts, contain bearings and joints that can wear over time. A rubber boot is supposed to keep dirt and particles away from these critical areas, as well as retain bearing grease. Most axle failures are due to rips and tears in the boot which contaminates the grease and allows excessive wear. Unfortunately, without lubrication the bearings and joints will wear quickly and the entire axle must be replaced.
A new inner seal is recommended by BMW (see link below).
F10 / F11 (11-16) > 528i xDrive N20 (2012-2016)
F10 / F11 (11-16) > 535d
F10 / F11 (11-16) > 535d xDrive
F10 / F11 (11-16) > 535i xDrive
F10 / F11 (11-16) > 550i xDrive
F12 / F13 (12-18) > 640i
F12 / F13 (12-18) > 650i xDrive