After attached to a carbon filter that fan will be 30 cfm maybe. Like pokesalot said, the 4' fan/filter combo will be more like 150 cfm after attached to the filter. More efficent and better for venting the room.
got mine from a used computer shop near me $5 for 4 inch and $10 for the 5 inch, then i used a 12v home phone charger matched the power and the ground, used wire nuts and placed in the box