First of all, they're all 10 inches or smaller, useless for any but apartment / condo dwellers who don't do serious cooking.

Second, some are non-stick. No sane person does deep fry in a non-stick pan.

Third, some are pretty stainless steel. Deep fry in one of those and you'll have to scrub it inside and out with oven cleaner - it'll look terrible. Iron and steel are supposed to develop a black varnish "seasoning", stainless is not.

My kadhai is a mere 14 inches, about the smallest size for general use. India Sweets and Spices down in Glendale sells them them up to about 36 inches. Mine is stamped out of a heavy sheet of steel, and I do mean heavy, it weighs 9 pounds.

A kadhai looks kind of like a wok, but is not at all the same. The radius is different and the sides are higher and more vertical. It is far better than a wok for deep fry, very much done in India, and for which I use it fairly often.

On the other hand, a kadhai is not so good for East / Southeast Asian stir-fry. Recipes from that region often ask to push ingredients up the sides while adding others in the middle. The sides of a kadhai are too steep for that.

Now I do use (but never for deep fry) a 13 inch tri-ply stainless wok, which would absolutely horrify any aficionado of Cantonese stir-fry - it's way to slow to respond to changes in temperature. That's OK, you can't really do Cantonese on a home stove anyway - though J Kenji Lopez-Alt has developed a way to fake it using a map-gas blow torch.

13 inches is a little cramped, but suits me most of the time, as I'm usually doing stir-fry for three or fewer people.

For more demanding work I have a 14 inch carbon steel wok by Atlas Metal Spinning of San Francisco - the best ever made. Unfortunately they no longer make them.

At the same time I bought that wok, 55 years ago, I bought the best Chinese cleaver knife ever made, by Dexter Russel of Massachusetts. I've used it often since then. It is still made, and a recent book by a top expert in Chinese cooking says that just about every skilled Chinese chef in the US uses that knife. They now also make a stainless steel version (at a lower price), but that's strictly for amateurs.

I seldom use this knife for Chinese recipes, but consider it, and a soft faced mallet, to be one of my kitchen essentials - see Chinese Cleaver Knife & Mallet.

And speaking of stuff in production for an unusual time, in the late sixties I purchased a Fluke 73 multimeter. It was just replaced by a new model about 2 years ago. That has to be some sort of record for electronic equipment. A support person once asked me on the phone if my multimeter was sensitive enough for what he wanted me to do. I said, "I don't know, it's a Fluke". His response was "Bastard!" - he apparently knew what a Fluke multimeter cost.

But for something really long lasting - I think it was in the Balkans, many years ago the grave of a lady from Paleolithic hunter-gatherer times, thought to have been a shaman, was partially excavated. It was found to have an amazing amount of grave goods, from an era when grave goods were rare. Recently, excavation was completed - and they found there was a second layer of offerings made at her grave site, 700 YEARS after her death. Now that is fame.