1. Widely Compatible- weed eater spool is compatible with BLACK and DECKER weed eater 2. High Quality Material- The string trimmer replacement spool uses nylon lines which is durable and flexible for fast cutting. Premium weed eater string with 21.6" easily cuts through grass and weeds . 3. Auto Feed System- The replacement trimmer spool automatically feeds the string to the trimmer. The auto feed system replacement spool eases the tedious work of hand-winding spools. 4. Suitable Length- The BLACK and DECKER string trimmer spool allows wider range of moving area that you don't have to replace it frequently. 5. Rugged material: High-quality ABS spool & durable polyamide nylon thread, flexible and long service life. Aerodynamic shape allows less drag for more efficient cuts.