What's the difference between the ML and ML PRO?

[Pocah]

I know I have asked this before and someone said the PRO has a higher RPM, but according to every specification I can find, there is absolutely no difference between the two! Obviously there must be something, so what is it?

[c-attack]

Weight. The "ML grey" twin pack are like most typical included fans for cases/coolers. No frills and lean on structure. Most notably the corners don't have the padding, but I think the real difference is in the weight. The ML-Pro frame feels heavier. Does it matter? Probably not for most people. If you are sound critic the heftier frame should offer more dampening. I feel the MLs strong point is in those middle RPM zones. Where a lot of other fans start to get loud, the ML can go another 200 rpm before it sound similar. And of course, it's black. Tends to sell well.