The F3.5 V2 features a new crankcase and heat sink design with larger heat sink fins for improved cooling. This new design makes the engine 22G lighter and 4mm taller. A new pull start utilizes a one-way bearing encased in a large 14mm hex for increased durability.The F3.5 engine will give you eye-opening acceleration and crazy top speeds! The engine is started by a simple pull starter system and the two-needle carburetor allows you to fine-tune the performance for any kind of weather or fuel.One added benefit of the Nitro Star F3.5 is that it's a race-legal .21-Size engine, which means you can drop down to your local track or Club and enter in a race as soon as you open the box! On the inside, The F3.5 has true ABC construction, with a chrome-plated brass Piston and cylinder surrounded by the lightweight aluminum case.