I have a fuller bust and purchased the size that the chart said I needed.  IT is accurate!  I got a S/M and whe I pulled it from the package I thought "now how will this fit me?".  I looked again and found an extension pannel inside the box.  Great idea!  You zip the pannel in the front and it extends the space between holes for the pump.  The only thing that is a tad akward is the fully adjustable velcro.  You want to adjust it to fit you then put it on. All in all a Great product.  It also came very fast to APO!