I'm a busty gal, this is a VERY padded bra, so much so that my buxom bosom does not even fill all of the cup, and it is in my size.  I have never needed a padded bra and after a certain cup size I don't think it's necessary and as for a tshirt bra, please you can see the outline of the bra cups because the padding is so thick.  I would wear this under ANYTHING other than a cotton or clingy tshirt.  It's comfortable over all, I don't know that I'm wearing it, but the preshaped cups do not really fit the shape of my bosom, but overall it's ok, just busty girls beware, there's a lot of padding up in there.