Don't forget to cut an intake in the door. For 4" blower should be at least 2 X 4" intake vents. I bought a 4" fan/filter combo off ebay. Thinking it was about $125 for both. The filter lasted until about week 2 of flower and I replaced it with a Phresh filter. That was $80. That filter even broke down near the end of my grow. I have to be stealthy so smell isn't an option. I bought a 5Lb bag of coconut carbon off ebay to repack the filters for next grow. Gotta have the speed controller. Mine is a router speed controller and it was about $20.