ROG Xpander is used to run 4 way SLI on the Rampage III Extreme. WHY does the Rampage III Extreme not support 4 way SLI you ask? Well to run 4 way SLI, you are required to use 2 Nvidia NF200 chips, which would make the board about $100 more expensive. 99% of the users out there do not even use 4 way SLI. For single ->TRI SLI users, having a NF200 CHIP can reduce your performance. THUS why we decide to make the Rampage III Extreme Cheaper and FASTER! For the 1% out there that need 4 way SLI to overclock, the Xpander is a win win solution! This will not fit in a standard case. Unless you are a case modder and plan to make a case for it, it is targeted for extreme overclockers and benchers.