What size trimmer line does my Shredder Joe SDJ616 use? Your Shredder Joe SDJ616 uses heavy duty 2.5mm trimmer line, the highest rated line for an electric shredder. You can always purchase replacement line (Model# SDJ616L) on our website. Related articles What type of string does this trimmer use? How large is the cutting diameter of my Shredder Joe SDJ616? What is the mulching capacity of my Shredder Joe SDJ616? Motor and Internal Parts Replacement Where can I get a replacement filter for my ash vacuum?