4x4 Standard (Nominal) Black Flat Top Post Cap - with 10 Year Warranty Made from high impact, remarkably sturdy ASA resin. The same material used in automobiles. 10 year warranty against fading, discoloration and warping. These caps are paintable and completely UV stable Quick and easy patented SNAP-CAP installation, built right into the cap! Fits a standard (Nominal) post. (3.5 x 3.5 up to 3.85' x 3.85').