In 2016, Hohner came out with the ACE-48 chromatic harmonica.
It encompasses a revolutionary new concept, allowing a player to insert wedge-shaped blocks from the rear into the main structure of the harmonica. Hohner writes on there website:
ACE stands for Acoustic Coupling Elements, removable inserts with which you can adjust tonal color and weight distribution of your ACE 48 to your personal taste.
The patent #DE102013021367A1 was granted in 2014.
In theory all kinds of different materials could be used as inserts such as wood, stone, metals etc.. They can be bought as a pack and the player can change materials if they wish.
Besides brass, Hohner currently offers separate wood ACE Elements.
In addition, Hohner introduced a new slider system called VarioSpring system: the VarioSpring system permits easy slide spring tension adjustment via a dedicated screw.
Chromatic Harmonica History 