... 72 hours.Widening manganese steel spring,can disperse force when the hinge closed.Strengthened .spring,thickness 2.5mm,Instead ... hydraulic system,longer life time,smaller volumeStrengthened spring,buffer hinge,bumper hinge.1, Strengthened adjustable screw can widen the ... life.2,Widening manganese steel spring,can disperse force when the hinge closed.Strengthened spring, thickness 2.5mm, Instead ...