This is a fan duct to cool the stepper drivers on the azteeg x5 mini v3. It holds two 30x30x10mm fans. The fans are offset and positioned evenly above the stepper drivers. Use #4 screws to mount it to the board. Use another #4 screw to clamp the two fans together.
The fans create a resonance, so im still trying to figure out how to quiet them down.