Good vs bad ... on the same filter model.
How about just some "bumps" with hair width slits in the center tube.
This is what all louvers should look like, but apparently it really is rocket science for some companies to figure out, lol.
How about just some "bumps" with hair width slits in the center tube.
This is what all louvers should look like, but apparently it really is rocket science for some companies to figure out, lol.