This is a 150 mm x 150 mm x 21 mm square tray with diagonal dividing wall. The dividing wall has a slight down curve. The inner edge at the bottom all the way around is rounded so you can easily pickup  small items from inside the tray such as button batteries, coins, screws, and washers. I have a sheet magnet on the back of mine and use it when I am working on electronics like my 5+ to keep small screws from rolling off the table. I use one side for screws and the other for the allan keys. 

Pictures shown was printed on Ender 5+ with a 0.6mm nozzle at 0.32 layer height in Eryone Silk Copper PLA.