https://www.techradar.com/news/apple-introduces-dual-sim-capabilities-on-new-iphones-with-the-intention-of-killing-sim-cards-altogether

Apple has played a big role in cutting the size of SIM cards from standard to micro to nano as well as introduce eSIM capabilities with the Apple SIM on the 9.7-inch iPad Pro a couple of years back. 

However, there’s been one area that Apple has been ignoring for a while now which is dual SIM capabilities and with the iPhone XS, Apple finally checks that box as well.