There are several different systems on the market. The multi tip lines have a 15' head. The RIO shooting heads are a 30' head.

Its nice to be able to swap out the different heads. They work great for me Bass Fishing and Salt Water. They don't cast as nicely and accurately as an integrated fly line. They don't work very well when fishing rivers for trout with the floating head.

For trout I prefer spare spools and integrated fly lines.