Simple and convenient installation will not waste your time and energy. High-quality and exquisite workmanship make it very sturdy and durable.The universal feature makes it suitable for most bicycle wheels. And the high strength and high hardness make it can be used for a long time.Made of steel material, it is very durable to use.The thread inner diameter of this product is 3.4cm.It is suitable for single-speed bicycles, electric bicycles, and folding bicycles. The smaller the number of teeth, the faster the speed increase. If the bicycle used 16 teeth before, the speed can be increased by 30% by switching to this 12 teeth.Item Name: FlywheelMaterial: SteelFeatures: Not Easily Deformed, Sturdy, Wear-resistantSize Details: Thread Inner Diameter: 3.4cm/1.34" (Approx.)Thread Depth: 1.05cm/0.41" (Approx.)Inner Hole: 1.8cm/0.71" (Approx.)Total Thickness: 2.65cm/1.04" (Approx.)Maximum Outer Diameter Of Flywheel Teeth: 5.3cm/2.09" (Approx.)Notes:Due to the light and screen setting difference, the item's color may be slightly different from the pictures.Please allow slight dimension difference due to different manual measurement.Package Includes:1 x Flywheel