Because there are a large variety of fly line tapers and weights, there are standardized
designations to identify various fly line types and sizes. The American Fishing Tackle
Manufacturers Association adopted a system of designating fly line sizes that is almost
universally used.
Example: WF8S
The first part of a line designation is the taper of the line, which is identified by two letters.
In this case it is the WF or weight forward.
Next is the number that designates the size of the line. In this case it is an eight weight
line. The weight of the first thirty feet of line measured in grains designates the size of the
line.
Last are two letters that identifies the type of fly line. In this case it is a sinking fly line. It
could be a floating line, one that sinks quickly, one that sinks slowly, or one that only
partially sinks.
These designations should appear on the box or packaging that the fly line comes in.
To review, a “WF8S” designation indicates the fly line is a weight-forward, eight weight,
sinking line.
Designations:
“WF” is the designation for a weight forward line.
“ST” is a shooting tapered line.
“L” stands for a level line with no taper.
An “S” indicates a sinking line.
“F” is for floating, “FT” for a sinking-tip line, and “I” stands for an intermediate sinking fly
line.