The Hummer H1 Alpha is a limited-production version of the Hummer H1, a civilian version of the United States military High Mobility Multipurpose Wheeled Vehicle (HMMWV). The Hummer H1 Alpha was produced from 2006 to 2009. It featured an upgraded 300 horsepower 6.6 litre V8 Duramax Diesel engine, upgraded suspension, and improved interior. The Alpha also featured a body-on-frame construction, larger brakes, power steering and an improved transfer case. It is considered to be one of the toughest off-road vehicles in the world.