These new versions (from 2021 onwards) have a hole in the top and bottom face with a black / white plastic plug. This enables you to power extra cases passively without the need for a Strom Passive module. When you remove the plastic plug, you can feed a cable through the hole and directly connect busboards together. This saves an extra 4HP of your precious modular synthesizer real estate.
If you also need some high-quality power for your system, look at our line of Eurorack Power products.
If you can’t be bothered with configuring everything yourself, just get the powered 3U case and you’re good to go!