This is a new Rubbermaid drain board. The dimensions are 13.81 in. L X 18.25 in. W X 2 in.

Some information from online:

Save time, towels, and counter space with the Rubbermaid Antimicrobial Drain Board. Sized to fit most dish rack drainers, the sloped tray is designed with ridges and a lip that hangs over the edge of the sink for optimal drainage without the mess. When the dishes are dry, this slim board is easy to store away. Built-in Microban provides antimicrobial protection that resists mold and mildew growth on the dish drainer.* Clean by hand with warm water and sponge or add to the dishwasher.