Material: cylindrical door remaining package is aluminum alloy, rectangular door remaining kit is stainless steelProduct features: Double spring design, springback smooth, gold and silver, solid power. The rebound force could be adjusted. Effectively lengthen the provider lifetime of the door, the door is made of metal, surface electroplating treatment, with corrosion resistance, durable, beautiful appearance and different characteristics! The tie rod is chrome steel solid material, upgraded and thickened, strong and durable, hard to damage.