Top plate fan mount option first seen on the 4.8NFT. Recommended with the Destiny/Roche/Rad-Tec "Freeze" 20mm fan. 

While similar in appearance, this is not the same part as our center shock mount. This piece takes shorter mounting screws, and the center hole has been drilled out to be a through-hole. Using the "Freeze" fan, the 4-40 x 3/8" button head screw taps its own threads into the fan.