Flow adjustable Fan Grill

If you want to reduce fan flow, you can use this fan grill.
I use sunhokey prusa i3. In my case, after I add additional nozzle fan(http://www.thingiverse.com/thing:891623), it was hard to reach 250 Celcius degree for printing ABS. I thought the original cooling fan (12V not adjustable) is more powerful on the right side configuration. So I decide to reduce flow rate using this fan grill.
After I use this, It was easy to reach 250 Celcius degree for ABS, also it is stable.