Allen Sports Urban Aluminum 1 Speed Folding Bicycle 6061 Aluminum Frame and a low maintenance single speed drive train deliver a great folding bicycle for urban environments One speed gearing for flat trails or small hills 451 MM Wheels deliver improved performance and handling over the standard 20" or 16" found on most folding bicycles Patented frame release levers allow quick and easy folding of bicycle in less than 8 seconds Patented wheel lock system secures the bicycle when folded and allows the bicycle to be rolled like a cart