You know when someone says something and you don't believe them because every washer and power tool out there is "heavy duty". I recall going to stores specifically designed for sewing supplies and bought the sturdiest zipper I could find. It broke... and broke again. Fortunately, these stores went out of business and I was led by the power of Christ to this zipper. It is so big and durable, I will probably never need another 30 inch zipper again. I can take this one out of my current jacket and put it right on my next new one like a mechanic would salvage engines out of scrap cars. If someone attacks me, I can rest assured that I have nunchucks and brass knuckles for a zipper handle. These would really hurt to get hit with. They also double as a bell jingling around so your dog always knows where you are. Although I'm sure it would void the warranty, I think you could probably pull a truck out of the ditch with them. In the nutshell, I don't know what size zipper I will need in my next jacket, so I really need you to keep buying these so they are around when I need them. I've never seen a zipper like this in my life and I wonder how the zipper standard got to be so bad. Support quality.