Durable White PVC Vinyl Internal Pyramid Post Cap For A True 4 Inch X 4 Inch Post | Single Pack | AWCP-INT-4 The Internal Pyramid cap fits internally on a true 4 in. x 4 in. post | Simple to install | Made in the U.S.A. Manufactured from high quality, durable PVC vinyl | Will not fade, discolor or warp | UV Resistant | Water Resistant | Limited lifetime warranty Perfect for a fence, deck, or mailbox post | Maintenance Free: Simply slide the Internal Pyramid cap into your post. Set it and forget it. | Use clear silicone (not included) for outdoor use to secure the cap (optional) Maximum internal post profile dimensions: 3.675 in. x 3.675 in. | Corner Radius: .25 in. | Total height: 1.5 in. | Overall Outside Dimensions: 4 in. x 4 in. | Color: white The Internal Pyramid post cap provides a clean, finished look to your deck, fence or mailbox post | Insert .75 inches into the post