The Martin & Co. Marquis 80/20 12-String Set are strings for any acoustic 12 string guitar. I don't own a 12 string, rather I recently purchased these strings for use on my Martin DX-1R acoustic guitar in Nashville stringing. Nashville stringing is when you put the octave up 12-string strings in place of the low E, A, D & G strings on your 6 string guitar. It makes for a really cool sound that is very similar to a traditional 12 string guitar. At the same time, it's a sound of it's own. For me, I wasn't really using my Martin guitar all that much of late, so I decided to do this to have an extra color guitar at home. I've used Nashville stringed guitars on recordings but never had one myself. It definitely helps if you put it on what was a good guitar to begin with, but if you only have a cheap back up guitar at home, I'd still encourage you to get a pack of these and string it up. I really love the sound it results in both for blending and singular settings. It makes sense for me to put Martin strings on a Martin guitar, but as you know it isn't always necessary to match them up. Having said this, I think these strings are a perfect blend for my guitar. I don't really know what a full set of these strings would be like on a 12 string guitar, but I do know I'll be using the standard strings left in the pack for stringing up my Martin again once I decide to switch it back to standard stringing (if I ever do that). However, judging by how the top strings feel, I'm sure the rest will follow suit. These are great strings at a reasonable price - definitely check them out regardless of what you're using them for.