The fly line provides the weight needed to load the rod while casting. The AFTM numbers describe the weight of the fly line, calculated in grains over the first 9.1 m (30 feet) of line and are described on the rod by # always followed by a number. If we use a fly line that is too light for the rod, it will not flex because it is not loaded enough. If the fly line is too heavy for the rod, it will overload it, causing it to flex too much and making casting difficult. Fly Line Profiles The first letters of the ATM standards classify the fly line as:

Uniform (level= L) – have the same diameter along their entire length

Double-taper (DT) = offers greater control and light poses on the water

Weight forward offset (weight –forward = WF) = easy to use for long casts with still delicate poses.

Shooting-head or shooting taper (SH) = used only for very long casts, especially on lakes.

Fly Line Density Fly lines can be floating, sinking, sinking tip, intermediate or neutral.