The Lawn-Boy 20 in. Self-Propelled Walk-Behind Mower with Sens-A-Speed automatically adjusts to your walking speed, saving timing and improving control. The Kohler XT6 OHV engine provides the power, efficiency and durability you expect, while the variable speed rear-wheel drive system gives better traction in all cutting conditions. The 7 in. front and 8 in. rear wheels deliver solid traction to easily maneuver around all types of terrain, while the multi-notched blade cuts grass into fine clippings for a clean cut.