feature: High-quality oil seal material to prevent oil leakage The piston rack is made of high carbon steel, which has been quenched and tempered by high frequency to prolong the service life of the product The spring is made of high-quality steel, which has been quenched and tempered by high frequency to prolong the service life of the product. High-quality aluminum alloy die-casting body, three layers of bright paint protection to prevent oxidation. Applicable temperature: -40 to 60 degrees. Easy installation good fire resistance Suitable for different kinds of doors Two-stage speed regulation range: 180-15 degrees, self-locking speed: 15-0 degrees 90 degree keep door open function keeps the door still when the door is open 90 degrees Latch continuous adjustment buffer function.