What are the differences between SRAM XDR and XD, and how do they impact compatibility with different types of bike components?

SRAM XDR and XD are two different cassette driver body designs used in bike components. XDR is newer and has a smaller diameter, allowing for a wider range of gears. XD is older and has a larger diameter. The main impact on compatibility is that XDR is not compatible with XD components, but XD is compatible with both XD and XDR components. Riders need to ensure they have the correct driver body design for their specific components to ensure compatibility.