This is BeefEater OEM Part Number 94174, which is a replacement Vaporizer Plate for the BeefEater Signature 900 Series grills. It covers half the grill as you don't need it for under the griddle part that comes with the grill. If you have an extra cooking grid (BeefEater 94125) so that the grills cover the entire cooking surface, you will need to order two vaporizer plates.
Details
This part is an authentic BeefEater part and is made of stainless steel and will last years.