The ERN is a measure of a rod's power. It is a measurement of the Common Cents System. A rating of 1.5 would indicate that the rod would load with 30' of one weight line. So, the low ERN tells you that the rod will load well with less than 30' of one weight line and make a good small stream, short casting, true one weight rod. However, it also tells you that if your average cast is going to be 30' or over, you may not find the blank to be as powerful as you want.