INJEN Short Ram Intake question

Just got myself the INJEN Short Ram Intake Turbo Pipe (IS1895). I was wondering what size air filter should I buy? is it a 4" or 5"? not too sure...

4" IIRC... actually, i'm pretty sure its 4

get K&N .

he does have a point... FIPK can never go wrong...

Are you running a gm mat? Cause otherwise it would be the same as any other filter for your car, the actual filter attaches to the maf not the intake pipe.