I also have had the staining problem. I live in FL and it gets hot and humid and that is when the problem is most noticeable. I had it with a Sun Mountain 3.5 and I now have it with a Ping Hoofer that is less than a month old. I was told by Sun Mountain that their technical people surmise that the pH of some people's sweat causes the problem to occur. With the Sun Mountain bag, I ended up using a sheepskin cover on the strap and that eliminated the transfer of the dye to my clothes. The Ping strap is wider so I'll need to find a wider sheepskin cover if i am to use the same solution.