The DS-KD-ACF3/PLASTIC is the three-module flush mounting bracket for Hikvision's DS-KD8003 modular door station range.
Flush mounting recesses the door station into the wall for a near-flat finish, and the bracket doubles as the back box — set into the wall at first fix, with the modules fitted afterwards. It is the tidier option for new build and for entrances where a surface-mounted panel would be vulnerable.
Three-module size gives room for a fuller build: a DS-KD8003 camera module plus two of the keypad, card reader, nametag or display modules. That combination is typical on apartment blocks and commercial entrances where both visitors and residents need their own way in. Fit a DS-KD-BK blanking module in any slot you are not using. For surface mounting, use the DS-KD-ACW range instead.