I'm very interested in buying a Steyr AUG A3 M1 mud with an extended rail. However, I found three separate NATO AUG A3 M1 mud models that all appear to be exactly the same but they have different UPC codes. I can't find a single online retailer that can list the differences between the three, and I can't find any information through Google. Can anyone tell me the difference between these three AUG versions? They're all the A3 M1 NATO mud version with the extended rail. They all look exactly the same in pictures. UPC: 688218739471 / SKU: AUGM1MUDNATOEXT UPC: 688218739013 / SKU: AUGM1MUDNATOL2 UPC: 688218739464 / SKU: AUGM1MUDH2 I can't find any resource that explains the difference between the three so I came here. Hopefully someone here is knowledgeable enough to educate me.