Refine edge brush in Photoshop CS6
The brush in refine edge/mask has no relation to normal brushes in the brush pallett. It has no attributes like shape dynamics, jitter, etc. It has no hardness or softness or opacity. It only has size.
To verify this, select a wierd non-round brush in the brush pallett. Then go to refine edge and notice the brush there is still round. Not the same brush.