Compatibility: Fits for AFS 23-37 trimmers. Nylon Line: The replacement spool is made of high quality 7075 aircraft aluminum. The nylon line is flexible enough and not easy to break, allowing for fast cutting and longer service life. Efficient Cutting: Allows the lines to stretch and cushion the impact on hard surfaces, and the aerodynamic shape reduces drag for more efficient cutting. Proper Size: The cordless lawn mower spool is 3.5mm in diameter, which fits perfectly with the cord hole and provides a wider cut. The square spiral structure has better flexibility and durability. What you will receive: The package contains 20 pieces of F016800431 black square wire, each measuring 37 cm in length and 3.5 mm in diameter. Note: The data are all measured manually, please allow an error of 1-3 cm due to differences in light and display, there may be some color differences, please refer to the actual item received.