Blue Pure 411 Replacement Filter Compatible with Blueair Blue Pure 411, 411+, 411 Auto and Mini Air Purifiers, Particle and Activated Carbon, 2-Pack

As far as knockoffs, this looks like the lowest quality one yet. I added pictures next to my previous (also knockoff) filter. The iner lining looks like the cheap styrofoam they use for packaging, and the glue didn't even hold till delivery, as it came out of the package with the inner lining loose. Now I'm not even sure if I believe it's filtering much. I suppose this is the classic you get what you pay for, although my previous one was in the same price range and doesn't look like it came from the dollar store.

I love these filters. I replace my filters every 6 months and these are great quality for the price and super easy to install!

Fit perfectly on my set of blueair filters. Seemed well constructed, the charcoal filter looked a bit less dense than the original, but all of the non-oem filters are that way. Given the price, I will be buying this again!!

I didn’t notice a difference between this filter and the original ones. Well, the only difference was price! These filters are much cheaper.

Seems to be a bit smaller then original but works fine so far

Everything

The first party filters will often have an odd smell due to the glue used in them off-gassing. I haven't had that issue with these, will never go back!