Hate having to wind nylon line onto your trimmer head? the Stihl DuroCut is your answer. With Stihl pre-cut Duro line, just whack them into the holes and trim away - the Stihl head is specially designed to not let the line back out!
FITS: FS 55, FS 70, FS 91, FS 111, FS 94, FS 131, FS 240, FSA 90, FSA 130, FSA 135