The STIHL 42821209701 Pump Piston Set is a genuine OEM replacement part designed for specific STIHL backpack blowers and mistblowers. This essential component is crucial for the proper functioning of the fuel pump system, ensuring reliable operation and efficient fuel delivery. Manufactured to STIHL's rigorous quality standards, this pump piston set guarantees a precise fit and long-lasting durability for models including BR 500, BR 550, BR 600, BR 700, BR 700 X, BR 800 C-E, BR 800 X, SR 430, and SR 450.