You are looking at the SWG Mk4 Golf vent gauge pod which is designed by SWG Motorsport to fit most Mk4 Golfs (excluding Bora and R32)

The pod is a complete brand new unit and allows any 52mm gauge or dial to be integrated into the driverside air vent, this is ideal for keeping thar O.E look to the interior but still allowing any 52mm gauge of your choice to be seamlessly incorporated into the Mk4 Golf's dash while still keeping any required airflow to the driver (ideal for mount a boost gauge for your 1.8T etc).