Designed for the most demanding tree care and forestry professionals, the STIHL MS 400 C-M is built with STIHL M-Tronic™ engine technology to deliver low-emission, fuel-efficient performance even under changing conditions. Unlike its aluminum piston-equipped counterparts, the advanced magnesium piston in the MS 400 C-M provides greater displacement, power and torque without additional weight. A long-life HD2 air filter means you simply clean it instead of replacing it, while a pre-separation system removes large debris before it even gets to the air filter, increasing run time between cleanings.