ROD FLEX INDEX (RFI)
The RFI is the action identify of your rod. If you love the feel a your rod and its action, if you love how the rod handles, then make sure to measure its RFI. With that information, you can benchmark other rods that you are interested in.
When we were developing the specs for the T100, we wanted to base is it on a quantifiable and objective measure. Unfortunately there is not industry standard. We found the Japanese rating system which is based on the ratio of stiff sections to soft (flexible) sections (e.g. 5:5, 6:4, 7:3, 8:2) to be very subjective. It also not based on a quantifiable formula that can be repeated and used to precisely compare different rods.
The system we adopted was based first on the CCS system. CCS stands for Common Cents System and was developed by Dr. William Hanneman to measure the stiffness and action of a rod. Specifically, CCS is the number of pennies required to bend the rod tip a full 1/3 the length of the rod (considered an amount that fully loads a rod). Measured by connecting a bag to the rod tip (Lillian) and filling it with pennies until the rod bends to the required amount. More pennies = more stiffness. The CCS was a great start but didn't completely complete the picture. The reason? Rods of different lengths may have the same CCS but have a completely different feel to their action. The feel of the rod, the casting feel can be quite different. The solution was the RFI, articulated here by Tom Davis of Teton Tenkara (RFI).
The RFI simply divides the CCS by the length of the rod in meters. The result is the RFI. The RFI provides a quantitative/objective method of comparing a rods action to any other rod. The following chart provides a quick way to interpret the RFI values.