Compatible with Ryobi Cordless String Trimmers: This string trimmer replacement spool is compatible with Ryobi ONE+: 18V, 24V, 40V cordless string trimmer models. Automatic Feed Spool: Weed wacker string replacements for weed eater is easy to use, automatically feeds the trimmer by centrifugal force, reducing the trouble of manually sorting the replacement trimmer line spool while working. Abrasion Resistant: Trimmer string replacements for weed eater is constructed with upgraded nylon polyamide material that has a tensile strength of over 100 pounds and is 30% more durable than other brands for a longer service life. Cutting Efficiency: The weed eater string replacements for is soft and flexible, allowing the line to stretch and cushion when impact with hard surfaces, and increase cutting efficiency by 50%, allowing each spool to cut more weeds. If you want the automatic feed to work better, the recommended solution is to apply powder to the spool, which will provide a small amount