I just recently bought what was described as "store return" "near-new condition" Otterbox Defender case for Note 4 on eBay.
I already had a genuine one that got on Amazon, and just wanted to try a different color, but I didn't really want to pay the full price.
What I received looked like Otterbox case at first, but upon a closer look I noticed a few things:
1. The material used is quite different. The knockoff feels like cheap plastic and the outer layer feels stiffer and does not have a rubber feel. Not sure how that may affect its protective qualities.
2. The fit is not perfect and the edges are not well-rounded.
3. The little circle that shows the production date is not very well stamped - looks blurred.
4. And more importantly, there is no serial number. Genuine ones have a sticker on the inside of the shell with a serial number for warranty. This one didn't have any.
However, this knockoff is very well made (for a knock off, of course). If I didn't already have the original one, I would never knew this.
So, beware that apparently there are a lot of counterfeit Otterboxes sold as genuine ones, and not necessarily cheaper.