Braided mono is what it says on the line. I read a little about it, but still don't understand the purpose for fly fishing. One thing that was said a couple of times was it was used with shooting line.
I had to look it up and went - DUH! It is a braid made of multiple monofilament lines. It's supposed to be supple yet stiff, so now I am just confused about the next thing I learned... how can that be?
A company called Blue Sky makes fly fishing leaders with a multiple-monfilament design, but I've never heard of a running line made like that. When using these leaders, you're supposed to attach your own single-strand tippet.
Generally it is intended to be used with a shooting head which is short (30ft) heavy fly line (floating or sinking) connected by a loop to loop. These are common in spey set up and this line is also used by Tenkara anglers. I'm not sure that Cortland is going to continue to produce this, however.
Was popular a number of years ago for building your own sinking fly lines. I guess they may still be popular for some applications. Coupled with a shooting head fabricated from a high density line such as LC13, it offered a method to make relatively long casts with a line that would get your presentation deep in a very efficient manner. Was popular on the Roanoke River during the striper run when the water was up and running strong and you wanted to target fish in 20 ft of fast moving water.
Though I've built them and used them, I'm with EvBlue when it comes to those types of water conditions I'm going with the spinning rod.
As far as what you can use it for, depending on how much you have available it could be used for flyline backing on a reel used for sunfish, crappies, etc where you don't expect to need alot of backing.