Whats the difference in rods?

[hitthebricks]

I see a lot of rods advertised as a IM6, IM7, IM8 rod blanks, what does that mean and how does that affect the sensativity, action, and other stuff? HTB

[upnorth]

The higher the IM number the more graphite modulus in the blank. It will be stiffer and able to transmit vibration(enhanced sensitivity) better. The blank will also be faster. The down side will be price and they are going to be more delicate and take much more care to keep them safe from breakage.

There is also the point of diminishing returns. I have built some rods on IM7 and they are nice, but I don't think I would go for the IM8 myself. I take care of my rods but don't like to actually baby them, I want to use them.