This guide is not foolproof, But can realy help in most case`s,
Ok im going 2 keep this simple,
question 1 to seller ; Does your item have a seam in the bubble? If they say yes there copy`s :-(
question 2 to seller ; Is the size label under the tounge sewn on? Most copys are iron-on square patches,
question 3 to seller ; Is there an official site where i can view detail`s of this item? They should have a product number and seller should refer you to the nike website(official one of course).
Also do an internet search on whatever there calling them,but when you do the search add the word "copy" or "fake" to the name that`s being used.