FIM Topping is a way to make your plants grow 4-16 branches in one stress session. Instead of pulling the whole top off you cut about 80% of it off, which results in more branches and a higher yield. FIM topping is recommended to people who top thier plants because in one session you get more branches which in turn cause less stress. The red line on the picture is about where you would cut for an FIM top. hope this helps Peace.