Difference Between ZF, BF1, BF3 & Electric Power ZF: With the ZF system, you must move the shift lever to switch between forward and reverse. The reverse gear is actively engaged. BF1: With the Brake Freewheel (BF1), you do not need to shift. You can drive forward and reverse simply by pedaling in the desired direction. At the same time, the integrated back-pedal brake allows you to stop gently and safely. BF3: The Brake Freewheel with 3-speed gear system allows forward and reverse driving without manual switching. The integrated back-pedal brake ensures particularly safe and comfortable braking. The 3 gears provide the right transmission for any terrain. Electric Power: The Electric Power system supports you with an electric motor while pedaling. You can adjust the assistance level to match your needs. A practical start assist makes pulling away easier, even on inclines. Safety and Warning Instructions: The DINO CARS STYLEZ is the go-kart where safety and comfort are paramount. The robust steel tube frame and pneumatic tires with ball bearings ensure a thrilling driving experience. The 6-position adjustable seat makes this racing go-kart suitable for children and adults from 5 to 99 years old. The front swing axle with extra travel keeps all four wheels firmly planted, even on uneven tracks. Another highlight is the extra-thick powder coating on the frame, which is forgiving of minor crashes. The DINO CARS STYLEZ features a robust ball-joint steering system, allowing you to cruise effortlessly through every curve. The chain is easily and conveniently adjusted using the user-friendly chain tensioner. The fully enclosed chain guard prevents injuries and protects the chain from dirt and grime. Additional welded steel reinforcements in the seat mounts prevent the seat from loosening. This is DINO CARS quality that pays off when you resell it. As you can see, the safety and comfort of the DINO CARS STYLEZ are uncompromising. assembly Instructions Download assembly instructions Technical Explanation of ZF Hub The product shown in the image may differ from the original.