Ego 3660582001 Replacement Compression Spring Compatible with Ego AH1300, AH1520, AH1522, AH1530 & AH1531 Trimmer Heads IMPORTANT NOTE: Older versions of ST1500F or ST1500SF Trimmers may have the AH1500 trimmer head which uses a different spring. If your trimmer head has green lines that must line up to put line into the head, then your trimmer head is model AH1500 and you need part Number 3660650001 Ego 3660582001 Compression Spring Compatible with for Ego ST1500, ST1500-S, ST1500F, ST1500SF, ST1500XY, ST1510S, ST1510T, ST1520, ST1520S, ST1530 and STA1500 15inch String Trimmers Ego ST1500 replacement spring has good elasticity, even if it works for a long time, it can restore its appearance, ensuring your long-term use, Manufacturer: Akfldms