When you want the best, this is it. Featuring Nikwax Hydrophobic Down to keep you warm even if things get wet and a ThermaCapture lining for advanced, super lightweight warmth, the three-season Antares HD can handle just about anything from early spring to late fall. The Antares HD has a water-resistant shell to shed moisture. SynergyLink Connectors integrate your mattress for optimal comfort and efficiency. It has also been updated with new Zoned Insulation, adding a light layer of sewn-through insulation to the bottom of the bag. This helps reduce drafts when joined with your mattress, and frees you to use your bag in a hostel or your friend's couch–wherever you don't need a camp mattress. We do recommend outdoor use however. It's just more fun that way.