DDR5 U-DIMM modules have the same dimensions and pin count as DDR4 modules. The most obvious difference is the position of the fool-proof notch. Also, DDR5 integrates I/O resistors with CMD/ADD resistors. Also, the appearance of DDR5 modules are cleaner than DDR4. In addition, you can see a PMIC in the center.

DDR5 vs DDR4 - Appearance

DDR5 modules provide two times more capacity than DDR4 by packing in more banks and bank groups. In addition, Burst Length and Prefetch are also doubled. And to ensure data integrity, they feature error correcting code (ECC) technology.