Using clear western red cedar, Nantucket Post cap manufactures some of the finest post caps and finials available in the industry. Cedar has a very long standing, strong resistance to mold and mildew. Its low density makes it less likely to swell, warp, cup or twist, compared to other soft and hardwoods. Due to the caps being installed horizontally on top of the posts, they receive the most sun exposure. So even though you may leave a cedar fence to weather naturally, we highly recommend treating not only the cedar caps but all wood species caps. Our stock Island Cedar Caps are sized to fit standard nominal wood posts 4 x 4. Inside width 3½ in. x 3½ in.