ALEKO ZG04E 3 1/4 x 3 1/4 Inch Post Cap for Gate Fence The Aluminum Post ball cap is made of carbon steel, it's self color, galvanized is also ok. It's used for Fence pillar, sliding gate pillar, swing gate pillar, etc. Ball Diameter: 77 MM Metal: Steel Galvanized. Aleko 84 x 84 mm (3 1/4 inch) Post Cap