I tried this .155" line on a Kwik HD trimmer head. The lines kept on flying off the head after less than a minute's use. When I looked for another HD trimmer head on-line, I discovered I couldn't find one that would accept .155" line, unless it was round in cross section. This stuff by Cyclone is hexagonal making it useless for me. I've returned the line. Buyers should be aware of the difficulty of finding a head that will work with this hexagonal line.