I used this in a project I built for my Grandson. He has other base plates but they were harder to move when he had built something on them.It is basically a tray with handles and you add the baseplate to the bottom.The child can build on the tray and when he has to move it just pick it up by the handles and put it away without having to dismantle the project.I used plywood for the bottom and top grade pine for the sides. This baseplate fit perfectly in a bottom that I cut 15 1/8 inches X 15 1/8 inches.Painted with a brush ( 2 coats) using a gloss Rustoleum paint . I have included a couple of photos .Yes, it's a grey 15" square Lego plate. But I seem to remember the "baseplates" being the same thinkness as a regular Lego piece. ...the base plate is a thin (1/16"?), flexible Lego baseplate that will allow you to build really big stuff, but it's tough to use on the "living room carpet" because it is so thin it flexes into the carpet when you try to press a "house" onto it. The result is that either only one corner of the house sticks, or it sticks fine, but all the other structures you've put on, flex off.Anyway, it's a vital item in any kid's (or adult's) Lego set....Building a Lego table for the kids using eight of these. Precisely what I needed but there is a large price variance for the same item within Amazon and buy limits that resulted in paying for 5 at the lowest price and 3 at a marginally higher price. Dimensions are actually 15 1/8" x 15 1/8" for those considering a similar project. Clearly must be used on a hard surface.High quality as all Lego products but price seems a little much for a piece of plastic. Would have bought at toy store to avoid shipping but they were out of stock. Had to bite the bullet since I needed it to make a Lego table for my granddaughter. Can't make her wait!I bought two and have on top of our coffee table in sitting room. Works perfect! Love the grey does not stand out in our modern living room.My 9 year old granddaughter loves Lego Friends. She is challenged by the larger kits, and at times likes to put several kits together. These base plates give her more room on which to build her creations. I think she may be an engineer someday.We needed a big base plate for a project for my son's school book report. This extra large baseplate was perfect for the lego map he built for the book he read. It came quickly, we are prime members, and was in perfect condition. It was exactly what we needed for the lego project.These are the largest boards made to date and I was told they won't make any more of this size. They are the only ones that are light gray. I hope the new version will be a lot larger but their keeping details secret until the new release.