Hole Size Needed Measures 30mm x 22mm Total Size Of Switch 32mm x 24mm Total Depth 42mm. A latched illuminated Delta rocker switch fog is a type of switch that has an illuminated light on the face of the switch which can be used to indicate the current status of the switch. The switch is usually used to activate or deactivate a fog machine and when the switch is in the latched position it will remain in that position until the switch is pressed again. The illuminated light on the switch will indicate when the switch is in the on or off position.