String trimmer line fits onto a trimmer head and whips through grass, weeds, and brush. It replaces depleted line or provides a different line material or diameter to suit specific applications. Smaller-diameter line cuts faster through thinner growth but snaps more easily than larger-diameter line, which resists breaking and cuts through thicker growth.

These string trimmer heads replace broken heads with new ones that will properly hold and deploy the trimmer line. They fit onto the trimmer shaft and spin the line to whip through grass, weeds, and brush.