This Light-weight high carbon steel frame mountain bike, ergonomic design, both quality and performance, anti-deformation, anti-stretch. 21-speed shifting system on-demand for uphill Climbing, downhill riding, or pure acceleration. Light-weight mini folding bike:Now you can take your bike where ever you go without the need for those pesky bike racks or risking the dangers of locking it up in public spaces. Portable use:Easy to fold, easy to store. Magnesium wheel:Light-weight and easy for riders to control. The wheels are durable and easy to wear out.