In a simplistic view of the history of marine lines, there’s been a progression from single braid manilla three strand, to double braid with the load being carried by the inner core, to today’s return to single braid but using high-tech materials, most frequently with 12 or more strands.
The new single braid lines can be super strong, small in diameter, and relatively easy to work with. They aren’t for use everywhere on your boat, some flatten out and don’t like to work in a clutch, some need UV protection, and some need the wear resistance of a cover. But for things like a cascade to turn a 4-to-1 vang into 8-to-1, they seem hard to beat. In more complex applications these lines are being used as sheets, halyards, and in control line applications.
There are more of these lines available all the time from a number of manufacturers. Some of the lines available today include Dyneema and Vectran lines like Amsteel Blue by Samson or Vectrus 12 by Yale, AS-90 made of Dyneema SK-90 by Samson, and Dynex Dux 75 by Hampidjan. While tensile strength is not the same thing as working strength, this stuff is pretty amazing. Comparing the tensile strength of 1/4″ lines:
Sta-set double braid 2,500
7×19 rigging wire 6,400
Dynex Dux 16,411
These lines are easy to splice using a Brummel splice.