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  • Writer's pictureChris O'Byrne

Fly Size, Finger Size

A Simple Comparison

When selecting a fly, we must take into account the shape, silhouette, and color of the natural creatures we are replicating. But size might be the most important aspect to consider.

Today we have a system of naming the size of flies derived from the historical manufacturing of wire. While this nomenclature might be confusing to our modern minds, or meaningless to less experienced anglers, you don’t have to memorize tables and tables of specifications. Until you can make sense of statements like… “A number twenty-two dry.” Or, “A size ­­two baitfish imitation.” Or, “A big ol’ three-aught.” you can compare the size of the flies, and the naturals in the water to your hands. As examples of this type of measurement, I offer these comparisons.

A size (or #) 20 hook is about the size of the lunula on your fingernail.

A size 10 hook is as big as your fingernail.

A size 4 hook is about the size of the first digit of your finger.

A size 2/0 hook does not quite reach to your middle knuckle.

And that big ol’ 3/0 fills the first two digits of your finger.

These guesstimates and examples are for hooks, tails on flies will add to the size. Hope that this comparison system will help you choose more accurately. Tight Lines!

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