1, fits all standard trimmer head. 2, long life, excellent strength. 3, made by quality polyamide& ... : round, square, star, heptagon, twist, sawtooth.3, available package: card head, blister, loops, donut, spool for 15m / 1/2# / 1#/ 3 ... # / 5# / 10#4, shaped cutting performance5, twist trimmer line for low noise.6, sawtooth line with pre-cut ...