IM-what? Demystifying rod materials

Editor's Note: This story is part of a larger package on Shimano gear. Click here to see more.

Graphite has long been the popular choice in building quality fishing rods. But there are several choices of intermedial module graphite used in fishing rod blanks. And it helps to know the difference when you’re selecting a rod.


Shimano’s rods are built with graphite varying from IM7 to IM10. The higher the number, the greater the cost. And the higher the number, the crisper and more sensitive the rod will be. IM10 will also be thinner than IM9, etc.

You can hear the difference when you tap a fishing rod on a hard surface. An IM10 rod will have a higher pitched sound than IM9 rod.

Crucial is the benchmark line of Shimano rods. All Crucial rods are made with an IM10 blank. Compre rods are made with IM9, Clarus with IM8 and Convergence with IM7.

TC-4 is a graphite-figerglass combination used in making Shimano’s crankbait, underspin and topwater rods. TC-4 is figerglass wrapped over graphite in four layers – graphite, glass, graphite, glass. It’s another example of Shimano innovation. The result is a rod with strength, durability and better flex distribution. It has the flex range of a fiberglass rod with the sensitivity and thinness of graphite.

Fiberglass rods are normally thick and heavy. The diameter and lightness of Shimano’s TC-4 rods are important distinctions.

Another important difference in Shimano rods is the consistency. All Shimano rods are put on a deflection stand to determine their variance. Five percent or less is the standard.

Try that with another manufacturer’s rods. For example, it’s likely you’ll notice a significant difference between two seven-foot, fast action, medium heavy rods. Then make the comparison with two Shimano rods of the same type. You’ll be able to see the Shimano difference for yourself.