Steel fuel tanks are commonly used in motorcycles due to their durability, strength, and resistance to impact and vibration. They are also less prone to damage from UV rays or certain chemicals compared to plastic tanks. However, it's always a good idea to verify the specific material used in the fuel tank of the Suzuki Gixxer by referring to the manufacturer's specifications or consulting with a Suzuki dealership or authorized service center, as designs and materials can change over time.