Usually the last digit of a blank # indicates what "power rating" the manufacturer assigned to the rod. This not only varies from company to company, but even the same manufacturer will assign different power ratings to the same blank that's sold under different applications.
Example---Loomis made two rods on the same blank--the SUR 1084S and the SWR 108-20. As a spinning rod in the "surf" application it was given a medium "4" power rating. As a casting rod in the "saltwater" application, it was given a light "2" power rating. Same blank--same butt diameter, same tip diameter, same taper, same blank weight, two different power ratings.
It's no wonder people get confused.
Normally the first 3 digits in a blank model # refer to the length in inches. You'd think that this would be a constant, huh? Not always--the Rainshadow SW108- series rods are actually 106" long, not 108"
