4x4 Post Cap (True 4") White Pyramid Top - 10 Year Warranty Fits a true (Actual) post. (3 7/8 x 3 7/8 to 4.6 x 4.6). These caps slide down the post 1 1/2" and are 5 1/2 x 5 1/2 at their widest point. 10 year guarantee against fading, discoloration and warping! High impact, remarkably sturdy ASA resin. The same material used to in automobiles! Quick and easy patented SNAP-CAP installation, built right into the cap!