Your bridge’s #1 grade southern yellow pine that has been pressure treated to resist decay and insect damage. As with all of our treated wood products, the wood is "KDAT" (kiln dried after treatment) to assure that it stays flat, does not bow or twist, and limits checking. It is highly suggested that you seal the railings regularly (every two years depending on your location) to maintain its appearance, or if you prefer a more rustic look you can allow it to gray and still keep the protection from the elements.