I have one on my 640 and the quality is awesome, it's beautiful. And strong. I've had one problem with it though, it wore a hole in the bottom of a brand new dry duffle in just 2 days, likewise the previous bag in a few days. It's because it's mostly open space, the bag rests on a very small surface area. I bought a plate of ABS on amazon and cut it to fit, shame to cover it up though. I'm sure it's more of an issue on the 640 because the vibes are pretty bad, but I mentioned it to my neighbor who said the same happened with the PMB on his 690.