Feature: The inertial flywheel for hot air engines is lightweight, making it easy to install and ideal for experimenting with engine models and gyroscopes. Replacement: This flywheel can be used as a replacement part for lab experiments or as a supplement to your existing engine accessories. Easy to install: With an inside bore diameter of approximately 6mm (0.24 inch) and thickness of approximately 1.4cm (0.55 inch), this flywheel is easy to install and use. Wide application: The electricity power generator flywheel has a wide range of applications, suitable for science projects, physical mechanical learning, and teacher demonstration tools in the classroom. Material: Made from high-quality aluminum, this flywheel is built to last and withstand the rigors of daily use. Size Chart: Outer diameter: 7.1cm (2.80 inch) Shaft diameter: 6mm (0.24 inch) Thickness: 1.4cm (0.55 inch) Package includes: 1 x engine flywheel Note: Please allow slight variations due to manual measurement and differences in display monitors.