I am not familiar with the Ariens trimmer, but I have the Cub Cadet ST100 which is a similar machine. The string that Cub Cadet makes (pre-cut square shape) works very well. I recently purchased Rhino-Tuff .155 line from Home Depot and while it did okay with just grass, it did not perform as well as the Cub Cadet string on thicker/longer grass and brush. You can also purchase .155 string from DR Mowers that will work with your type of machine.
