A plant or vegetation cutting device which comprises a rotary cutting head and at least one cutting filament or string extending radially from the head, such that upon rotation of the head, the string is extended by centrifugal force and cuts through the plants or vegetation. The string is profiled in a generally uniform manner along its length and it comprises a main body whose width/height ratio is between about 1.2 and 2. A co-extruded cutting appendage may be joined along the leading edge and/or the trailing edge of the main body.