4" can filter?

Looking for advice on what I should use for a 4" filter. It would attach to my passive air intake (which is rigid dryer venting) that my outtake fan pulls air from my veg cab, into my flowering cab. I've seen square ones and round. Im not concerned about smell or anything, this would mainly be for any dust/debris floating around.Right now I have panty hose covering it. Thanks in advance on any tips.

Can use a few choices from airbox inline filter, dust shroom filter, 4in carbon filter or make box with insert for a house central heat filter you can get from any hardware store. Many ways to do it beyond this and all work just depends on budget, space, and skill.