I’d like to add RockAuto as a peer to McMaster. It’s auto parts, and somehow uglier than McMaster, but damn if it isn’t the fastest no nonsense website I’ve seen for parts.
I can drill down to a specific part for a specific car in seconds, and see pics of the product, part numbers, specs. It’s lovely.
Rockauto is one of my favorite things in the world. The site is a perfect case study in how to make a UX that's ugly as sin but has evolved to be a million times more usable than anything the "minimal sleek modern UX" crowd could ever come up with.
You always roll the dice with aftermaket parts of course, but my experience has been that they usually don't sell utter crap like you'll find on Amazon and eBay. They make some effort to verify that the parts are not bottom-of-the-barrel because they don't want to deal with returns and after all, they are car people themselves.
My favorite thing that I like to tell people that have not heard of RockAuto yet: I can buy a full of wiper blades for my two cars for about the same price as ONE mid-quality wiper blade at Walmart.
I can drill down to a specific part for a specific car in seconds, and see pics of the product, part numbers, specs. It’s lovely.