D2 racing are fine, they are a rebrand of another popular and well known make, I can't comment on the surface area of the pistons as it does not specify, but the quality in general of d2 racing products are pretty good.
Also note that although it does say it 'could' fit under 15" (I emphasise could) it depends very much on the offset and the design of the wheels. Personally I don't like running with such little clearances as it's difficult to clean, I have to take my wheels off if I wish to give my calipers a good clean.