This is the Traxxas Flywheel with Magnet (35mm). This Flywheel is for use with telemetry set-ups on several Traxxas nitro products, such as the Nitro 4-TEC 3.3. This flywheel is equipped with a magnet that enables a sensor (sold separately) to read RPM data.
Note: This item requires a TQi radio system with Docking Base (#6510) to access telemetry data. Some models may include telemetry-ready components as standard equipment. Inspect your model before purchasing this item.