Made of thick and extremely durable stainless steel, these angle brackets are ideal for outdoor use. I used them to reinforce the railing on our second deck. Four stars, however, because the bolts aren't long enough or heavy enough to match the strength of the struts. They are more like furniture quality. what you find on the bookshelf. If you want to take full advantage of the robust construction of these brackets, you will need longer, heavier stainless steel screws, and these are expensive.