C.F. Martin Acoustic Guitar Martin Flexible Core FX 80/20 Bronze .011 - .052, MFX-675star rating 4george byichFebruary 15, 2010Tried these strings to see if they were comparable to the Newtone heritage low tension. I was pleasantly surprised at the tone. 80/20 strings are recommended for vintage acoustics or guitars built in a vintage style and they sound great on my Martin om28v. Martin markets these strings for players who want a softer feel but they don't seem as bendable as the Newtone strings. However for half the price you can't go wrong.