Used low temperature&resist freeze hydraulic pressure oil, keep the door smooth when it is-40° cold. After the special design, control the bearing of the spring hinge, lighten the strength when open, and close the door. High strength and leak prevent configuration where use to extend the life of it. As it can avoid mangle. and oil leak by strength or strong wind from outside. And it can be adjusted 15mm length and 15mm width. Portrait adjust ±5° when calibrating zero sites. It makes products more easily.