It has silicon fibre filling which is hollow for that extra warmth. This filling is used on some of the Top Models. This filling gives a great performance and is among the top fillers for bags.Using the most moder of design and manufacturing techniques gives this range warmth with comfort. This filling will spring into life when unrolled and will not stay compressed.The Sleeper Lite is a lightweight good performance sleeping bag giving lots of warmth. Tough and hard wearing with a soft touch finish.This is an super into bag and fits into the Snugpak range.