This allow to completely remove the original "blowing" fan deflector and replace it by a "sucking" fan deflector... yes, it sucks... ;)
Anybody that print with ABS know (I guess) that any kind of uncontroled air flow on the piece lead to problems.
To avoid that, I usually flip the blowing fan to suck the air through the heatsink fins instead of blowing it in direction of the piece. The result is a most constant temperature of the printing area.
You will have to decrease the temperature of the extruder (I had to decrease mine from 250°C to 220°C on the TEVO Tornado)
The adjustable part is for the additional fan (The one that still blow the air in the direction of the printed part when needed)
By the way, in case you wonder what is a sucking fan... it's just a flipped blowing fan ;)