No, not all weed trimmers operate with the same strings. Several parameters like string dimensions, spool length, the material of the trimmer line, etc., are mainly to be checked before making a purchase. These determinants play a significant role in the efficiency of the trimmer line. Refer to the manual provided with your weed trimmer. The trimmer line must be compatible with the trimmer head. All these parameters will be defined there. However, a weed eater string with close enough features may also work in the absence of the mentioned string. Larger diameter and round cord strings are widely used due to their robustness yet flexibility. But it may cost you higher and produce more noise than those with lesser diameter.