Can't yet confirm the durability of this alternator but I am very impressed with the build quality. and fits. This is a perfect replacement for the original block (01 BMW 740il) and comes complete with a new O-ring. The pulley spun well with no hesitation/backlash or noise whatsoever. I'll let you know if there are any issues in the future, but for now this has been a surprisingly inexpensive alternative to an OEM unit.