Resistors mean business when they have certificates (Patreon)

5 months lead time and 200 bucks for these beauties! The metal can ones are hand-crafted and hermetically sealed. And that's only accessories in the quest for an ultra-stable voltage reference.

The total accuracy of around 0.01% is secondary, it's the low temperature coefficient of ± 0.05 ppm/°C that makes these so special.

https://xdevs.com/article/kx-ref/