The Eurorack 1U format module is a realtively new concept and something that Intellijel have been pushing as a standard. It allows for smaller 1U height modules to be added generally (in the Intellijel cases) across the top (or bottom) of a 7U (3+3+1) Eurorack case, or in the case of Makenoise through the middle - with the CV Bus module.
Intellijel make a variety of 1U modules to fit this space and the Multi-FX 1U is a multi-fx with Reverb, Delay and Chorus - stereo in stereo out, plus clock input. It is 24HP wide.
It features 3 modes:
Priced at $129
https://intellijel.com/shop/eurorack/1u/multi-fx-1u/
Developments for Korg's instrument have been slow but promising.