Fits a true (Actual) post. (3 7/8 x 3 7/8 to 4.6 x 4.6).Estate 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 in automobiles!Made in the U.S.A.Quick and easy patented SNAP-CAP installation, built right into the cap!Fraction of the cost of comparable wood caps.Contractor and bulk pricing available! Made in the USA These post caps fits actual 4x4 post (4"x4"up to 4.6"x4.6") rough cut posts also fits Trex post, Vinyl post ,and metal 4" post