Hinge #3, 14 gauge, black powder coated. Goes between sections 3 and 4, higher up the door where more offset is needed to keep the roller tracking through the curve. The powder coat finish resists corrosion better than plain steel. If the door binds or makes a popping noise around the middle sections, check the #3 hinges for cracks or bending. Replace with the same number. they are not interchangeable, each number puts the roller at a different distance from the hinge barrel.