Spring is Zinc plating on the harden steel,surface electric galvanizing,Sturdy and Anti-corrosion,enhance the weather resistance and lifetime of the porch swing spring kit.The spring locates between the overhead support and swing chain to provide a more comfortable, softer feel to porch swings, free-standing swings, hammocks and hammock chairs.The Swing Springs are PREMIUM 304 Stainless Steel HEAVY DUTY Spring,will absorb the shock and preserve the longevity, Reduce noise, vibration and stress,Slight Extension SpringPorch Swing Springs are Made of heat-treated stainless steel springs, one piece weight capacity of 500LB, Introducing a unique even suspension system can increase the elasticity of your beloved hammock chair.The Hammock Hanging Kit Safe for Hammock Chairs or Ceiling Mount Porch Swings,Yoga, porch swing, hammock, sandbag, hanging chair, lamp, sling trainer, awning, sling trainer, chair,swimming pools & backyard , cave & more, Whether Indoor & outdoorCan be widely used in various occasions.