Thumb Brakes

[Marshy]

The rear master cylinder is hidden behind the carbon heel guard, which is a pity because they are sooooo sexy! Mario got the Complete kit with two IMA master cylinders.

[Turbo]

It's worth pointing out that Mario's thumb position ended up to be quite different to mine. Mine was pretty much as pictured but Mario holds the edge of the bars, when riding, so he adjusted the thumb paddle to be closer to the middle of the grip.
I think it's this sort of adjustability that is making it feel so natural to use. You just don't have to think about it, it's right where your thumb is!