iPhone XR

/* 1792x828px at 326ppi */
@media only screen 
    and (device-width : 414px) 
    and (device-height : 896px) 
    and (-webkit-device-pixel-ratio : 2) { }

iPhone XS

/* 2436x1125px at 458ppi */
@media only screen 
    and (device-width : 375px) 
    and (device-height : 812px) 
    and (-webkit-device-pixel-ratio : 3) { }

iPhone XS Max

/* 2688x1242px at 458ppi */
@media only screen 
    and (device-width : 414px) 
    and (device-height : 896px) 
    and (-webkit-device-pixel-ratio : 3) { }

Looking for a specific orientation ?

Portrait

Add the following rule:

    and (orientation : portrait) 

Landscape

Add the following rule:

    and (orientation : landscape) 

References:

• https://developer.apple.com/design/human-interface-guidelines/ios/visual-design/adaptivity-and-layout/
• https://www.paintcodeapp.com/news/ultimate-guide-to-iphone-resolutions