Lego Part: 91405. Base Plate Building Board 16 x 16 Studs - Dark Grey
Part: 91405. "This is a LEGO 16x16 baseplate, specifically part number 91405. It's a light gray square with 256 studs arranged in a 16x16 grid. Authentic LEGO. 16x16 Base Plate with solid studs. X1 Dark Grey.