I use them for a lot of things on the farm and they are wonderful to have on hand. For their price they are great. They are just as strong and durable as the ones I bought at the pet food store or hardware store. I don't know what they call "heavy duty," but they've helped me put a latch on the coop, fasten fence panels, make makeshift lines, hang up buckets of food and water, and have endured being outside so far. the rain is pretty good. If they're a bit difficult to open, I just spray WD40 on them and they pop right off. I wouldn't use them to hold a large animal or anything heavy, but they're pretty comfortable.