1.Compatible with GreenWorks 2101602, 2101602A, STBA40B210, 2101602, ST40B410, BST4000 dual line string trimmers.Includes 3*Dual line string trimmer spools.This is an aftermarket of generic part.2.Spool line length 16ft provide a wider range of mowing.High-quality ABS spool durable polyamide nylon thread, flexible and long service life.3.Twisted line for added strength and durability. Use centrifugal force and aerodynamics to reduce drag and achieve fast cutting.CNC machine cutting and winding, save time from cumbersome manual winding, reduce damage for string trimmer and not get stuck during cutting grass.4. It is necessary to wear goggles and long pants to avoid injury from spilling lines;Turn off the trimmer before changing, installing, or removing the spool.4. Only Suitable for tender weed grass. Tough and strong weeds please use blades to trim.