Fitment: compatible with C1MS237, FS40, FS50, FS50C, FS56 string trimmers. For additional models and years, please refer to the product description. Traps dust for cleaner operation: this air filter blocks dust, grass particles, and debris from entering the engine, helping keep the internal system clean and supporting smoother performance in dry or dusty conditions. Supports consistent airflow: acts as a dependable engine air filter to promote balanced air intake and efficient fuel combustion, helping maintain steady engine power during mowing sessions. Improves engine longevity: reduces buildup of harmful particles that can wear engine parts over time, maintains cleaner airflow, and lowers internal friction for long term reliability. Key attributes: robust filtration media designed for outdoor use, compatible with standard trimmer housings, and engineered to enhance engine performance and dependability. Use scenarios: Mowing in dusty or windy conditions where airborne particles are common. Working on sandy or loose soil where debris intake is higher. During midseason maintenance or when engine performance declines to restore steady airflow.