These pre and post filters are fine and the price seems great. I noticed that these non-original filters get dirty faster, especially the post-filter. So they are much cheaper but require more modifications. I think the reason the post filter gets dirty quicker on generics is because their pre filters let a little more dust through which then goes through the motor and then into the post filter. . Just my guess! They are very well priced, fit and work well which is why I give them 5 stars.