This is a coil spring with a coil shape processed into an arc shape (bow shape) when free, and is generally used in clutch dampers, etc. Arc springs have the advantage of simplifying the structure of the clutch damper, reducing the number of parts and contributing to weight reduction. Through our design, evaluation and manufacturing technology of arc springs tailored to the needs of our customers, we have been able to create highly reliable arc springs that are highly durable and permanent set.