The MS 261 C-MQ has all the same great features as the MS 261 – low emissions, high fuel efficiency and performance – for professional users and homeowners with large jobs. The MS 261 C-MQ also includes advanced STIHL M-Tronic™ engine management system. With STIHL M-Tronic™ an onboard microprocessor digitally monitors and automatically compensates for changes in your work conditions including elevation, temperature, fuel quality, varying octane levels and dirty air filters. The end result is maximum performance across a wide range of cutting conditions without making any manual adjustments. The saw also features STIHL Quickstop® Plus, an additional chain braking feature designed to stop the chain in less than one second when you completely release the rear handle.