Comes 95% assembled, all you need to do is install the front wheels, handlebars, pedal and saddle to complete a 27.5-inch SIRDAR mountain bike and enjoy the ride. It is made of aluminum alloy body with high carbon steel parts, such as the handle bar and the chain. These sturdy materials can protect the bike from damage and are strong enough to withstand any harsh environment. In addition, the tire pattern is wear-resistant and has strong anti-puncture ability so the bike is designed to last. It is made with 3 gears front derailleur and 9 gears derailleur that deliver 27 speeds of ultra smooth shifting.