If you are looking for a size beyond the standard 4X4 or 6X6? With these post caps you have a variety of options.
The Victoria Copper High Point is available in 5X5 (two opening sizes: 4-5/8" X 4-5/8" and 4-7/8" X 4-7/8"), True 6X6, 8X8 and 10X10.
Victoria High Point post caps are also available in True 6X6 in Stainless, Pewter and Black.
The Newport series offers a 4X6 post cap in the High Pyramid and Classic styles.