For a long time when I would go looking at fishing rods I would get confused by the various desigations on the labels. It wasn't the lure weights that were confusing, it was the designations such as: Ultra-Light, Medium, Heavy, Slow, Fast, etc. After doing some research I sorted out the designations and came to a better understanding of how rods are classified. These designations don't apply to fly rods, they have there own system for classifying the fly-rod weight and action. Rods are classified by two factors: the range of lure weights, and the amount of flex in the rod when it is loaded with the lure.
The rod weight is a pretty straight forward designation. It uses such terms like Ultra-Light, Light, Medium, Medium-Heavy, and Heavy. So a heavy action rod would probably have a lure weight range starting at 1oz and going up from there, while an Ultra-Light may have a lure range that starts at 1/32 oz and goes up to maybe 1/8oz. You probably get the idea.
The rod action is a little different. As I said earlier, it classifies the amount of the rod that flexes when it is loaded with a lure. The general designations are Slow, Medium, Fast, and Extra-Fast. Manufacturers may use some variation on the the wording, but their words should translate into this basic system. Slow action rods flex across the entire length of the rod up to the grips. Medium action rods flex over about the upper half of the rod, Fast action rods flex over only about one-third of tip, and Extra-Fast rods flex over only about one-fourth of the tip. Each type of action has its application and different people may use different actions for the same purpose.
Personally I prefer to use a Fast, or Extra-Fast action rod for most fishing. If I am jig, or texas-rigging I prefer to use an Extra-Fast tip for the sensitivity. If I am mojo-rigging I prefer a fast action because it allows the fish to load the rod before I set the hook. I very rarely use a slow action rod although they do see a lot of use. The "Noodle" type rods used by Steelhead fisherman would be considered a slow action rod. They allow the fisherman to use lighter line while fishing because the rod help cushion the load on the line. One note, however, the slower the action of the rod, the harder it is to get a good hookset because less force is applied directly to the fish.
I hope this has shed a little light on rod action and rod weight. I know the research taught me quite a bit.
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