I go through bump heads pretty fast during the season, probably 2 a month. I like to keep the string long and I've got a lot of fences to trim, etc. Problem is, it gets expensive to buy new bump knobs that often. Anyone have a suggestion as to where to buy them in bulk, or cheaper than retail. I think I usually use the 25-2. Just to be clear, I go through them so fast because the bump knobs wear out and go flat pretty quick. Cheap plastic.