The 4 season bag has an extra wide built-in expansion panel in the zipper that allows the bag to increase in width for more comfort while warmth is maintained. The Softie Insulation which was developed uniquely by Snugpak uses super fine synthetic yarns bound with special resins which create a true down like feel for the user. The staple yarns mimic the compositions of natural insulation.
Need a sleep mat to insulate from the ground? take a look at our range here.