Compatible with Ryobi Cordless Trimmers: This replacement trimmer spool is compatible with Ryobi ONE+: 18V, 24V, 40V cordless trimmer models. Automatic Feed Spool: The weed wacker string replacements is easy to use, automatically feeds the trimmer by centrifugal force, reducing the trouble of manually sorting the replacement trimmer line spool during work. Abrasion Resistant: Trimmer string replacements is constructed with upgraded nylon polyamide material that has abrasion resistance. The line has a tensile strength of over 100 pounds and is 30% more durable than other brands for a longer life. Cutting Efficiency: The weed trimmer string is soft and flexible, allowing the line to stretch and cushion upon impact with hard surfaces, and increasing cutting efficiency by 50%, allowing each spool to cut more weeds. The package contains 6 strings for Ryobi, 1 spool cap. If you want the automatic feed to work better, the recommended solution is to apply powder to the spool, which will