public float inertia { get; set; }

Rotational inertia controls a Rigidbody's resistance to changes in _angularVelocity. It is similar to how _mass controls a Rigidbody's resistance to changes in _linearVelocity.

The rotational inertia is automatically calculated based on the Rigidbody's _mass position relative to the _centerOfMass. It can also be specified explicitly by setting this property in the same way _mass can be set.