I have just got the US Military Modular Sleep System (MSS) made by Slumberjack , for use in Lapland and I have to say that I am very impressed with it so far.
1. Gore-tex Bivy Bag – Three Layer laminate mummy design bag cover for integration with the Modular Sleep System (MSS) for cold – wet conditions. The snap closure system allows each bag to snap to the Bivy. Fabric: Waterproof and Moisture Vapor Permeable plain weave nylon, with baffled nylon zipper closure. Color: Woodland Camouflage Pattern on the top, Camo Green ground shade on the bottom.
2. Summer Sleeping Bag – Mummy design for temperate climates of 0 to 10 Degrees C as a single bag. Snaps to the Bivy for use in slightly colder-wet zones. Insert the Intermediate Bag inside for colder extremes. Fabric for the shell and lining ripstop nylon with water resistant finish. Insulation Fill continuous filament resin bonded polyester. Features an adjustable hood and baffled nylon zipper closure.
3. Intermediate Cold Weather Sleeping Bag – Mummy design for colder weather climates of 0 to Minus 23 Degrees C as a single bag. Snaps to the Bivy for use in colder-wet zones. Insert inside the Patrol Bag for extreme cold environments. Fabric for the shell and lining ripstop nylon with water resistant finish. Insulation Fill hollow continuous filament resin bonded polyester. Features an adjustable hood and baffled nylon zipper closure.
4. Compression Stuff Sack – Numerous straps with ladder lock buckles tighten and compress the system. Nylon draw cord closure with barrel lock.
I slept out last night using the intermediate bag and bivy bag and found it to be incredibly warm. It rained at about 2am, but with the bivy bag close over me, I did not get wet and there was no excessive moisture inside the bag from my breath.