After a recent incident which put a major scratch across the barrel of my Remington 7600, .243 Hunting Rifle, I decided to try out a touch-up pen to keep the barrel from rusting. After a short search on Amazon.com, I ordered the Birchwood Casey Presto Gun Blue Touch Up Pen. Once it was delivered I scrubbed down the scratched area and set to work with the pen, I was surprised to see that it was a clear acid/chemical mix as opposed to the odd colored sharpie I was expecting, but as soon as the tip touched the barrel, the wide scratch simply faded away! it wasn't a perfect fix, but I had to extensively examine the area to find where the damage took place. I'm not saying this was an absolute, good-as-new fix, but after 2 treatments I had forgot where the scratch was. I have since used the pen on a few other lesser scratches on this gun and a few others. When I purchased this I was just looking to find a quick fix for my old work horse of a gun, and instead found a new product that has found a permanent home in my gun safe.