I have a Western Mountaineering Megalite bag regular size that comes in a 7x13 stuff sack from WM. I need to pack this smaller than that. What size compression sack should I get and how small do you think I can reasonably get to with a compression sack? I am open to any manufacturer --but would like to have an S to S or Granite Gear if possible. Thanks!

I'd have to agree with Mike on this question. I too got a stuff sack with my bag that's about the same size. I bought the S2S compression pack (small) and can pack my bag down to the size of slightly larger than a grapefruit. With the bag alone I have no more compression strap left to cinch up. It's pretty dang neat. I have been trying to save space in my 3000 c.i. Golite jam2 pack, which is why I went with the compression pack over the regular roll top closure. I've totally gotten rid of the stuff sack that came with my tent aside from the one for the poles. I now stuff my tent, footprint, and fly into a regular rolltop closure S2S drysak then throw that sack into the small compression sack listed here along with my sleeping bag. Talk about crazy space savings and packability. Of course I had to rethink my packing, but once I got that dialed up it's almost like my pack grew more space. I highly recommend these compression event saks, not only for the waterproof usage but it can save you mad space in the end, which meant everything for me getting ready for the AT.

My bag came with the a similar 7x13 bag, and I found that putting it into the XS took too much time and effort. I use the S and like it a lot. The compression sack swallows the bag easily, and then I can cinch the straps down to get it pretty small. I haven't measured it when it's fully compressed, but it's a little bit smaller than in the stuff sack it came with (football-size instead of bread box-size).