Harbor Freight tools are made in China and often one would be better served by cutting the picture of the tool out of the ad and attempting to use that. iPhones are also made in China to a very high spec. Chinese is not synonymous with crap. This is good, because damn near every drug we take comes from there.
Always nice to see someone else understands how manufacturing works!
China can produce products just as accurately and just as usable as anyone else, but when they do they cost the same. Chinese manufacturers therefore offer cheaper alternatives built to a lower spec in order to gain massive market share.
Unfortunately IP doesn't seem to mean much in China, any number of European and US companies have moved manufacturing out there, taken the time to work with the factories to get them to produce the quality they need to the specification they need, only to realise that the same factory has also started making the product to the same drawings but using lower spec materials, wider dimensional tolerances (so less wasted product to throw away, the customer gets it!), cheaper finishes etc. etc. and is undercutting them by supplying them to the same market as grey imports.
So what do you get when you buy a brand name air filter made in china? You get something that meets the OEM dimensional tolerance and materials requirements which will seal properly in your air cleaner housing so it defintiely filters the air.
When you buy an unbranded (or unrecognised) chinese grey import what do you get? Do you get something from the same factory with lower quality checking applied, that may or may not meet the dimensional tolerance and seal properly, does it have lower spec materials (larger pores for dirt to pass through, less strength so deteriorates more quickly), is it a copy from another factory who have reversed engineered it with no idea what the dimensional tolerances or material requiremetns are, or are you simply buying one that failed the OEM suppliers quality check and the factory stuck it in their own brand box instead of in the skip....???
That HF tooling is a nice example - a lot of their machines come from Shanghai Industries, you can trace them to many other cheap outlets and brands in the UK and US (one UK site even sells them under the manufacturers name). People have mixed experiences, bolts that break or holes that are misthreaded, burrs on machine surfaces and slideways etc. etc. whilst others have none of these - low quality doesn't mean every product will be crap, it just means the measure of whether it is crap enough to be rejected or not is set quite low.
I can think of 2 companies in the UK that offer these machines at a higher price, they import them ex-factory, strip them and remove the storage grease, remove burrs, sort out threads and bolts etc. and adjust the machines so that they work as intended and will cut to a good level of accuracy and repeatability (1 of the companies also sells them in the ex-factory condition to do yourself if you want to spend less). Another company goes to a similar level of trouble and fits digital readouts, stepper motors to the controls and adds a whole CNC package. Underneath you have a cheap machine which is probably maligned in reviews all around the world, yet when that company has finished with it, you have a low budget but very useable CNC machine which gets great reviews. So the Chinese manufacturer ends up with a wide range of markets and price points but can keep on building the machines cheaply so as to offer something for every budget!
Obviously that doesn't really work with air filters - if the silicone seal doesn't fit your cleaner housing, you can't really fettle it to fit!
The important thing to understand is that when we complain about made in China, we are actually complaining about low price goods - if you want it to fit better, you have to pay more because the factory will have to scrap more of it's output and the price differential to Europe or US will reduce dramatically - it really is that simple!