Sleeping Bag Overfill – Extra Down Insulation for Western Mountaineering Bags

Boost your sleeping bag’s performance with the Sleeping Bag Overfill, an optional upgrade that adds extra 850+ fill power ethically sourced goose down throughout your bag’s fully baffled chambers. This custom modification increases warmth by approximately 5°F, making it ideal for colder conditions, high-altitude trips, or anyone who simply prefers a warmer night’s sleep.

In addition to the immediate warmth boost, an overfill helps maintain long-term loft retention. Over time, even the highest quality down can lose some loft due to moisture, body oils, and repeated compression. By increasing the amount of down inside, your bag resists these effects longer, preserving its thermal efficiency for years to come.

Each sleeping bag model has a pre-determined overfill amount tailored to its design, ensuring the best warmth-to-weight ratio without overstuffing. You’ll simply choose your bag model and add the correct overfill option when placing your order.

Please note: Because the Sleeping Bag Overfill is a custom modification, overfilled bags are not eligible for returns or exchanges. This ensures each upgrade is built specifically for your needs.

Whether you’re preparing for a colder expedition or just want extra insulation for shoulder seasons, the Sleeping Bag Overfill is a lightweight, effective way to extend your bag’s comfort range and longevity.

Below is a list of eligible sleeping bags and the associated cost for this optional upgrade.

Bag	Overfill Weight
SummerLite, MegaLite, UltraLite, Alder MF, Apache MF & GWS	2oz
TerraLite, AlpinLite, VersaLite, Sycamore MF, Badger MF & GWS, Antelope MF & GWS	3oz
Sequoia MF & GWS, Kodiak MF & GWS, Lynx MF & GWS, Ponderosa MF	4oz
Bristlecone MF, Puma MF & GWS, Cypress GWS, Bison GWS	5oz

To specify your overfill please ensure that you have the proper bag and then select the overfill.  If you have questions please contact us prior to ordering.