The STIHL MS 171 is part of a new generation of lightweight STIHL chainsaws with reduced emission technology – a significant benefit for users because it saves fuel even as it cuts exhaust emissions.  The MS 171 also has the STIHL pre-separation air filter, which can extend filter life up to five times over previous models.  It features side-mounted chain tensioning for safe and easy chain tensioning and Stihl’s anti-vibration system.  Great for cutting firewood or for felling small trees.