I've used these strings since around 1990. They last me forever. DR takes the string core of the wrapped strings and stretches them to the tension they will be when in tune and then wrap the string. Then releasing the string tension causes the windings to wrap tighter making them take longer to stretch out to "dead" and there for last longer on your guitar.
Medium strings are .13-.56
Light strings are .12 to .54
Their mediums are listed MH (Medium Heavy) but rest assured they are true mediums. DR Used the term Medium on thier .12-.56 guage - go figure
Rare Phospher Bronze
Phosphor Bronze Acoustic Guitar Strings. Low tension...the sound is loud and warm.
The Rare phosphor bronze acoustic strings are departure from the standard, good quality bronze string currently available...not necessarily better, but possessing a new, different, and stronger “voice”. When DR set out to produce a string with new characteristics, our goal was to redesign contemporary thinking about what phosphor bronze can do for a good acoustic guitar. Hand-carved arch-tops and dreadnaughts and good steel string acoustic guitars of rosewood, maple, and mahogany seem to benefit from a distinct improvement in tone, depth, and sustain with Rare phosphor strings. Players who want a fatter and louder sound, as well as a deeper bottom (who like to hear their guitars ring out) will appreciate the Rare phosphor tone, sound, and feel. According to our heavy-playing bluegrass friend, three time national guitar picking champion Steve Kaufman, Rares last an unusually long time. Steve recommends DR to all his students.