Squash your gear down to 1/3rd and keep it dry! eVENT® fabric is totally waterproof and really actually breathable (you can feel the air coming out!) allowing you to squish the air out and keep water out.
While Sea To Summit could make a lighter compression sack, it wouldn't handle the stresses involved with squashing gear down by a third! Sea To Summit trimmed down webbing and buckles and made the sack more user friendly with a unique cap construction.