There's a few different sizes and models available now, both in 1 and 2P. The sizes they provide are accurate, so just measure based on your needs.
Also a second for the Megamat being the single finest sleeping surface ever created for
best mattress topper for side sleepers. There's now a thin model, a standard model, and a thicker model. The middle thickness is the sweet spot. Also, the Nemo Roamer (again, two sizes) is pretty much as comfortable, but easier to deflate and packs into a smaller size.