I was told that the grain window of my 7wt switch rod was 185-350. When asking vendors about the weight of the lines they sell and the weight of them, I was totally confused. Is the grain weight of a fly line the weight of the 1st 30 feet or 40 feet or is it the weight of whatever the mfg states is the length of the head or what. I can't seem to find a good explaination of what or how the standard is applied to different fly lines. I would rather not trial and error which line would be best. I'm just beginning and would like to start off with the right line so when I have problems, I will know it's me and not the equipment. Thanks in advance.