The stratosphere (/ËstrÃ¦tÉËsfÉªÉr, -toÊ-/) is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. About 20% of the atmosphere's mass is contained in the stratosphere.
The chainsaw is a highly effective and efficient tree and branch cutting power tool. It works with an engine, referred to as a power head; powering a metal chain, driven by a centrifugal clutch, with a chain moving around a groove in the guide bar at fast speeds.
With an advanced low-emission engine technology, the STIHL MS 391 mid-range chainsaw improves fuel efficiency by up to 20% compared to previous models. The new air filtration system requires fewer filter changes, allowing for longer run times. Improved fuel efficiency and fewer filter changes save you time and money.