The jeans in the pictures seem to be authentic, in my opinion. Be careful though, if you look through the seller's feedback, you will see some complaints from buyers where this sellers shows pictures of authentic jeans, and then sends fakes. Also, if you look through the seller's past completed items, several of his jeans have been, in my opinion, fakes. I guess it's up to you whether you want to trust the seller and that he will send you the jeans he posted, or if you want to rely on his reputation and stay away. As for the sizing, it depends on how the 27/28 fits you. If you squeeze into them tight, most likely you won't be able to fit into a 26. If the 27 is loose on you, then you can probably fit into these. I weat a sz 30 men fairly loosely, can squeeze into a 29, but is uncomfortable for me to wear a 28. Hope this helps.