This was on my home when we bought it and looking to reuse since I have a lot and it’s functionally okay. It measures 1″ x 5.5″ and is fairly heavy. I am thinking it is PVC? It doesn’t look or feel like the composite decking I’ve seen in videos. Also no signs of wear or rot despite being left untreated in full sun/rain for many years. I’ve read that PVC decking is lightweight while this feels pretty solid (about 2.5 pounds per foot).