The Stihl 11251605451 Brake Band QS2 is an original equipment manufacturer (OEM) replacement part designed for the chain brake system of various Stihl MS series chainsaws. This critical component ensures the safe and effective operation of the chain brake, stopping the chain rapidly in case of kickback or emergency. Manufactured to Stihl's rigorous standards, it guarantees precise fitment and durability for models including MS 029, MS 039, MS 270, MS 271, MS 280, MS 290, MS 291, MS 310, MS 311, MS 390, and MS 391.