Rods are made out of a variety of materials including fiberglass and graphite. Some rods are marked with IM6 or IM7 or similar. The IM stands for Intermediate Modulus. As the IM number increases, in theory, the rod 's stiffness increases as well. The interesting thing to note is that that IM6 and IM7 are actually trade names from the Hexcel Corporation. There is not industry standard, so manufacturer to manufacturer their is nothing that would cause two different IM6 rods to be in any way similar in build or strength.
Freshwater to Saltwater is a advertising gimmick in certain ways, but salt water rods due are often made from better materials to resist rusting. However, there is no guarantee that it will last longer.
Capt. Craig Copeland
Licensed by the US Coast Guard
2013 Nautic Star 2110 Shallow Bay Boat
Humminbird HELIX 12 CHIRP MEGA SI GPS G2N
Nautic Star Boats Pro Staff (nauticstarboats.com)
Redneck Fish'n Jigs Pro Staff (redneckfishn.com)