M6 Black Spring Lock Washer, Stainless Steel, Black Coating Split Lock Washer Elastic Gasket, for Screws Fasteners, 50PCS

I didn't test these to see if they really are 304 steel or anything special for measurements, but they worked for what I needed, and they met the key features I needed (I.D., O.D.). So they get the 5 stars because I don't see how they will fail in my use case.

I bought these M10 lock washers for woodworking. After using them in multiple projects, I am happy with their durability and value. One major plus is the thickness and quality of the black paint. Despite placing and removing these lock washers multiple times, the black paint has stayed on. None of the lock washers are rusting or discoloring the woodworking projects they secure because of the high-quality paint job. Thumbs up to the manufacturers for not cutting corners on this. For the price, the lock washers function exactly as needed. I would buy them again for interior woodworking projects. For users who require painted lock washers suitable for exterior projects that can withstand the elements, I'm unsure if these lock washers will meet your long-term needs. I did not use these washers under constant sunlight, freezing/high temperatures, or environmental moisture. Those factors take a serious toll on any black paint.

These will work out great for a decorative plaque I am making for a customer

Great product, great price, great service

As expected from a washer