There are not.
The size of the C-shaped cabinet is 100% determined by the customer. The direction and size of the hollow space can be customized completely according to the layout and needs of the customer’s home.
For example, many housing estates are equipped with building intercoms and light switches at the entrance of the unit. Designers will take these factors into consideration and adjust the cutout during the design phase. You can choose a design without a back panel or pre-cut holes in the back panel.