I have a ProCell deck with Trex railing which I had installed around 2005. ProCell was bought by AZEK. It is located in New York. The deck & railing gets black and green mold, especially on the north side on the railings. Corte Clean makes it disappear! It takes it right off. I like to power wash first, then let it thoroughly dry. The composite manufacturer recommendations of soap and water; forget it! It doesn't work. I've been using Corte Clean for years. I use to buy it locally, at 84 Lumber, but the store no longer carries it? The bags were always damaged and out of date? I forgot to clean it last year, so it looks a little worse this year. I just ordered more. This stuff is great! I recommend it to everyone. Thank god I found out about it from a lady in Florida.