Do they/will they be making this in a mummy shape? I'd like one that will fit into my big agnes mummy bag.

For clarification, the regular size NeoAir will fit into any of the (non-petite) Big Agnes bags that take rectangular 20" X 72" pad. Some Big Agnes bags require a mummy-shaped pad; the NeoAir will not work with these bags. The Large NeoAirs will not work in most Big Agnes bags (the pad is too wide), except for the spacious Big Agnes "Park" series. Here's a chart of Big Agnes bags and their respective pad sizes: http://www.bigagnes.com/Products/Specs/Bag FWIW, I use my NeoAir in my B.A. bag, and couldn't be happier. It does take some work to get the (thick) pad in the sleeve, but if you do it with the pad partially inflated, it's not too hard. But if you are camping in real cold weather, this system can get a little cold (since Big Agnes bags don't have insulation on the bottom). Otherwise (i.e., above 20-30 degrees) this is a killer system.

I have two Big Agnes mummy bags and a regular size NeoAir. Fits perfectly, though to save yourself a little trouble, I would stuff the mat inside before you start blowing it up (or blow it up just a little). Otherwise it's a lot of push and pull.

It only comes in rectangular sizes. For your BA bag, it'd be best to stick to the pads they engineer to go with it. Their air chamber pads aren't quite as impressive but still get it done: http://www.bigagnes.com/Products/ProductFinder/Pad/filters/34