This is Evga's little trick to get an ACX cooler onto your GTX Titan Black.
Currently, the GTX Titan Black is the fastest single-chip graphics card that money can buy. Unfortunately, that is only true for stock clock speeds, as many custom GTX 780 Ti cards still outperform it because of factory overclocks. These overclocks are possible because of the custom coolers, and unfortunately, Nvidia has restricted AICs from applying their own custom cooling solutions.
Fortunately, those among us who truly care about the ultimate performing graphics card are also quite good with a screwdriver, and thus not afraid to mount a different cooler onto a graphics card. Evga has made this possible, and quite affordably so.
For $39.99 you can order an ACX cooler from the Evga website, built specifically for the GTX Titan Black. It'll take you a couple of moments and patience to install it, but Evga has provided detailed instructions for how to go about it.
Do be careful though – it's safe to assume that this will void the warranty of your GTX Titan Black.