Quality is a two way street. Sometimes you don’t get what you pay for either.
Dad put himself through school working at a plant that made oil and fuel filters.
Monday and Tuesday they made brand X.
Wednesday they changed the paint color for the cans, and the boxes in the packing machine and produced brand Y filters on Thursday and Friday.
Spent my entire career supporting manufacturing facilities and processes around the world. I can’t judge by the quality of the products because I don’t use most of them, but I can speak to the quality of their management and production processes.
You would be surprised of my unbiased ranking of the worlds quality leaders.
Having said that, when buying products I look for two things.
1. A product specification or data sheet. Not a marketing brochure, but an actual data sheet. No data sheet you go to the back of the line.
2. A product actually made by the company whose name is on the product, ie not an outsourced product.
Sierra Marine‘s manufacturing facility is where?
To answer the OP question, I suspect the threads on the filter where “stamped“ instead of “roll formed”.
