21 inch aluminum frame Trek 4300 with front shocks. Staton-inc gear box with Robin-Subaru 2 stroke engine. This is the best motorized bike setup you can buy. It uses a gear box and a chain to drive a custom rear wheel with sprokets on both sides. This combo is used in rental applications with units having over 50000 miles. I paired this engine up with a nice trek bike and used it to commute to work. I would pedal half-way for exercise then crank the motor and ride the rest. Will go 30 mph with current drive sprocket. You can change the sprocket for more top or low end. Nothing to engage when you want to use the motor, free wheel on sprocket allows you to pedal whenever you want. Many upgrades to bike: Cateye computer, Gooseneck extension, Nice comfy seat, bottle cage,and more. You can't ride this thing without a smile on your face. Less than 300 miles. I was given a company vehicle so I don't use it anymore. Located in South Florida. $600 OBO PH: 772-260-0046