Acoustic Guitar Strings Medium - Heavy (13, 17, 26, 34, 45, 56) Hi-Beam 80/20 acoustic are designed for extra brightness, to cut through the ensemble playing of bluegrass musicians, as well as derive extra clarity from heavily braced, or dull sounding guitars. Wrapped upon a hex core the new Hi-Beam 80/20 acoustic are handmade and handwound for great tone, and increased longevity.