You'll know by the price. The factory ones are $400-$500. Most of the panels are manufactured in the same place, not real great quality but useable. The major differences are the lines aren't as defined and the material doesn't seem as heavy as the original. One word of caution, when you receive your item, make sure you inspect it good before signing the delivery slip. Your ONLY means of getting your money from the carrier. I lost out big time when the people at the UPS store signed the paperwork and then later we discovered the panel was damaged in shipment. Mine came from Goodmark (very poorly packaged, loose inside a huge box) and they use BAX shipping, Bax will not do a thing about the damage, even though the box looked damaged, when the UPS guy mentioned it to the driver, the driver said that it will be okay, if they find a problem they can file a claim. He was right, we did file a claim, no money though. It must be written on the delivery paperwork. A lot of dialog but just thought I'd share that just so someone else doesn't get burned.