【DIMENSIONS】 Thread Size: M10x1.0mm reverse thread (left-hand) Hex Size: 24mm outer / 17mm inner Material: Durable steel for extended service life 【FUNCTIONAL & VERSATILE】 Perfect for securing blades and heads on string trimmer gearboxes and brush cutter gear heads. Ideal for garden maintenance, landscaping, and agricultural trimming work, helping boost your tool's reliability and working efficiency. 【DIRECT REPLACEMENT FOR OEM PARTS】 These collar nuts are exact replacement accessories for original weed wacker nuts. Compatible with a wide range of S tihl models, including: FS Series Models: FS25-4, FS45, FS55, FS55C, FS55R, FS55RC, FS55T, FS56, FS56C, FS56R, FS56RC, FS56RC-E, FS66, FS70, FS70R, FS72, FS74, FS75, FS76, FS80, FS80R, FS81, FS85, FS86, FS87, FS87R, FS88, FS90, FS90R, FS91, FS91R, FS100, FS100R, FS100RX, FS110, FS110R, FS110X, FS110RX, FS120, FS120R, FS130, FS130R, FS131, FS200, FS200R, FS250, FS250R, FS-KM, FS65-4, FR108