Over 500,000 times open and close testing, at least 96 hours salt spray corrosion test, 100% inspection.This spring door closer can be used on doors up to 150 lbs Keep Quiet & Safe:Use these door closers to convert hinged doors to self-closing ones and you dont have to worry about your kids escaping from home or your pet dogs/cats running into your room Widely Application:Door closer is suitable for household doors, gates, agricultural fences, garden fences and various hinge doors, saving time and effort The door closer is made of aluminum alloy material,metal rod with smooth pulley,which is antioxidative, anticorrosive, waterproof and durable Adjustable Tension :The spring door closer can be easily adjust the tension to adjust the closing speed,and both left and right doors can be applied in these automatic door closer Easy to Install:Equipped with installation instructions and accessories, you can also refer to our pictures for installation