The DS-KD-ACF1/S is the stainless steel single-module flush mounting bracket for Hikvision's DS-KD8003 modular door station range.
It does the same job as the plastic DS-KD-ACF1 — recessing the door station into the wall and acting as the back box — but in stainless steel. That is the version to specify where the entrance is exposed, publicly accessible or likely to be knocked: a street-facing door, a communal entrance, a commercial unit. The steel frame is what stops the panel edges being the weak point once the modules are fitted.
Single-module size takes a DS-KD8003 camera module on its own, for a video door station with one call button. For builds that add a keypad, card reader or nametag module, use the DS-KD-ACF2/S or DS-KD-ACF3/S. For surface mounting in stainless, see the DS-KD-ACW/S range.