Metal Springs: Manufactured using high-quality raw materials. Offered in both round and square wire options for customer choice. Exhibit excellent spring stiffness and outstanding tensile/compression/torsional performance. Endure fatigue testing and durability checks for over ten thousand rebounds. Air Springs: Feature a dual safety air-tightness design ensuring stability. Equipped with a quick assembly design for easy installation and usage. Optional anti-loosening safety locks are available for extra security. Stable structure with exceptional durability.