Hori Kuro 24mm SILENT Pushbutton
Hori's entry into the parts market started with their Kuro pushbuttons. These pushbuttons were thoroughly tested by their pro sponsored player Sato who won numerous tournaments, including Capcom Cup.
These 24mm pushbuttons are quite rare to say the least. Based off of the Kuro design, the silent feature is added for that stealth, quiet activation.
This would be a unique pushbutton for those Hit-Box users.