Click here for a review of the MegaMat. 

And here's a short exerpt from the review: 

Be warned, we’re not talking ultra lightweight, minimalist bivying. No, instead envision cush road trip truck livin’ and deluxe basecamp snow camping. EXPED has created one of their top of the line sleeping pads to be four inches thick, 30 inches wide, and 6.5 feet long. Put two of them side-by-side and you have a queen sized bed! Because the EXPED Mega Mat 10 LXW sleeping pads have straight side walls and fit flushly together, we were able to do just that. The rectangular shape of the pads also make it so that you don’t have any fault lines between you and your partner like you would with mummy shaped pads. They fit together like bricks.