852339 Play Rug is a set that was released in 2008. It is a play rug that is made of fleece fabric that keeps bricks in place. It is mostly 39" by 39" inches and is used for building bigger sets. If you are planning on building something like the Death Star Model or something else big, you should buy one so you know where all your pieces are. It is blue and green and has a picture of some LEGO bricks in the middle. It is great for cleaning up so you do not lose any pieces. And the best part is it's only $19.99.