Mountain Bicycles are design for riding rough off-road trails. They have flat or upright handlebars, and a very low gear range for pedaling up steep trails. Most mountain bikes have some type of shock absorbers or suspension. Mountain bikes with front suspension only are called hardtails; mountain bikes with both front and rear suspension are called full-suspension bikes or duallies. Mountain bikes with no suspension are called rigid. Mountain bikes can be outfitted for use as touring or commuting bikes, although they would not be as light or efficient as traditional touring or commuting bikes. Fat bikes, with their extremely wide tires, are included in the mountain bike category.