Our flat top deck caps come in both nominal and actual sizes and are backed by our 10 Year Guarantee. 4x4 Post caps come in two different sizes, so be sure to measure your wood posts before ordering. Standard, pressure treated 4x4 posts generally measure 3.5 inches. Rough cut, untreated, and composite 4x4 posts generally measure a true 4" or larger. Don't worry though, even if you order the wrong size, we have a 30 day return window and will take them back with no hassle.