Controllers are really small these days and fit just fine in the gaps between keys (see link below for a typical example). It’s almost certainly mostly for the

Controllers are really small these days and fit just fine in the gaps between keys (see link below for a typical example). It’s almost certainly mostly for the battery. https://rama.works/updates/2020/4/24/m50-a-pcb-inventory-2-bands-rw01-parts-iced-dampeners https://rama.works/updates/2020/4/24/m50-a-pcb-inventory-2-b...