The main difference lies in the design of the transmission system and gear ratio.
1. Single-speed Shimano flywheels usually have only one gear, no transmission system, and no free wheel. This means that when the wheel turns, the gears and pedals also rotate together, and the rider cannot hold the pedals stationary while the wheel continues to rotate, like on a regular bicycle.
Ordinary flywheels are usually equipped with a transmission system, which can change the riding resistance and speed by switching gears. At the same time, ordinary flywheels are usually equipped with free wheels, that is, the wheels can continue to rotate without pedaling.