The 9155011 Nickel / 9155011B Black is a Single-Module Flush-mount Frame for use with 9155014 flush mount box.
The 9155014 Flush mounted box for walls or plasterboard for 1 module is for use with 9155011 Flush Mount Frame. The box cannot be used for surface installation.
Price quoted below includes Flush Mount Frame + Flush Mounting box.