http://www.tacklewarehouse.com/rodselection.html

http://www.furnacebayrods.com/tech.htm

"Modulus- A measure of applied load (stress) that it takes to deform a material in its finished process state."

"Modulus: As stated above, modulus refers to the stiffness of the graphite, not the amount of material used or the number of graphite fibers incorporated into the sheets. Buying a rod based solely on the modulus rating is a mistake because other factors must be considered. For instance, you don't want the stiffest rod for light line techniques or cranking. In addition, other qualities must be incorporated in the graphite itself and the rod must be designed correctly to ensure the best performance and durability of the rod. The other components that go into a quality rod can also add significantly to the cost."

"IM6, IM7, etc.: These are trade names for particular graphite produced by the Hexcel Corporation. These numbers are not industry standards or an indication of quality, especially since other companies use the designations to refer to graphite not made by Hexcel. At best, they allow you to compare the quality of the material used to build different rods by the same manufacturer. You can be confident that the IM7 rod would use better graphite than the IM6 rod if both are made by the same manufacturer. It's more difficult to say the same about rods from two different companies, since they could be made from material from completely different manufacturers."