The auto feed replacement spools of 1.5mm diameter line will eliminate the hassle and time spent hand-winding string trimmers. These spools are for use in the Sun Joe model # TRJ600C cordless 2-in-1 Lithium-Ion trimmer/Edger. They utilize centrifugal force for maximum performance. The line is durable nylon for tough cutting and long life. There are three spools, each with 14.76 feet of replacement line on them.