I own 2 of these bras. They're great.  They separate and encapsulate (sp?) with the inner layer, and the outer layer works like a compression bra.  The adjustable straps and band really help me get a good fit. I wear a 32DD in Calvin Klein bras (my fave for daily wear), and have to order a 32D for these bras.  I run 2-3 miles a few days a week, so I would say that this bra is good for high impact.  It took a few tries to find the right size, but definately worth the effort.  Later found out that they carry the Maia at my local running stores, should have tried it on there.  :)