I'm assuming it's referring to armored seams - basically where the tank's seams (usually only the vertical ones) are protected by a thin strip of glass to prevent things from cutting into or burrowing into/chewing through the silicone. I know a lot of people like them so they don't accidentally tear into their silicone with their razors while cleaning. I have no personal experience with armored seams though, so I can't really offer my take on them, but - OP, if you are talking about armored seams - there are plenty of threads on here discussing them that you can look through to get an idea of if people like them or not. Just type in "armored seams" in the search box and plenty will come up.