Our sleeping bag lineup is carefully designed to cover a full range of temperatures, but there are occasions where a little extra down is warranted. We can add up to 4 oz of overfill to many of our sleeping bags before they are finished, at the cost of the extra down ($23/oz for 900+, $25/oz for 950+). We DO NOT offer overfill on our -40°F Snow Goose and -60°F Snowy Owl sleeping bags. Keep in mind that any overfill in a sleeping bag is non-refundable in the event that you need to return the bag. Adding extra down to a sleeping bag is not an option available through our online ordering system, so please contact us if you need to place an order with extra down fill.