After the down stream nox sensor failed on my C Class I purchased this replacement. It came super quick and a genuine Merc boxed product. Fitted it in 15 mins with a nox spanner also purchased off eBay for £12. I was a little hesitant that the quote the engine management light would go off in 100-200 miles….The light went out after about 100 miles and 4 days. Great and all at the fraction of the cost at Merc.