The Expert Sleepers ES-5 is a Gate/Clock/Sync expansion module for the ES-3 (from version Mk2 on). The connectors of the mk3 version are equipped with multicolor background lightning.
It piggybacks on one of the host module’s stereo channels to provide eight gate/clock/sync/MIDI outputs on the ES-5 itself, plus further expansion headers to connect up to six expansion modules e.g. the ESX-8GT Gate Expander, the ESX-8CV CV Expander or the ESX-8MD MIDI/DINsync Expander. This means you can add 48 digital outputs to your ES8/9/3!