I've bought three lots of fake CK 365 trunks off here lately from different individuals despite having read lists of positive feedback from happy customers. If you didn't have the real thing to compare them to you might well be happy as they're not bad undies, admittedly, but they just aren't right. Often sold in lots of two or three pairs (or more from the Far East usually).
Things to look for specific to 365 trunks as follows:
The real packaging is in those anti-static bags that are transparent on BOTH sides, front and back. The fakes have at least one side completely opaque (can't see through the packet at all) in a thicker cheaper plastic too. There's also a cardboard insert into the real ones.
Stitching and hem:
The hems on the real ones aren't flat, they have a rounded lip as though a beading runs through the hem, stitched in. The stitching is also a give-away. The genuine ones have really compact stitching like an elongated italic 's' —the fakes is more spaced out like it's been done for speed.
The sizes are also wrong. A large fake comes up like a genuine medium.
I really would recommend you buy at least one genuine pair from a proper retail outlet to compare before deciding to keep these fakes. The sellers all seem happy to offer a refund as they can then sell them on to other unsuspecting people. Are you going to report a fraud when you have no proof once your items have been returned for a refund? At the least you should demand a refund of your return postal costs or report them to ebay.
Hope this saves you some wasted money!
A further caution (which you only become aware of once you've been stung and need the 'paypal protection') is that under paypal rules you are obliged to provide documented proof from an 'expert' that the item is fake, on company headed paper. How you would go about this is anyone's guess. It would seem to favour the fraudsters. You would think they would accept comparative photos of one real item against the fake item, but no. Therefore, don't rely on paypal if you're suspicious of an item before bidding thinking you'll get your money back. It's down to you to pay to have it shipped to the manufacturer (if they even provide that service) and you won't be getting that cost back from paypal even if they rule in your favour.