Mountain Hardwear Down Upgrade Review

"I own a Blue Kazoo down bag from The North Face which is rated to +20 degrees F. Instead of buying a new down bag for colder conditions, I purchased the Mountain Hardwear upgrade which is a +40 deg F bag by itself, but can be zipped into another bag to give an additional 25 deg of warmth. My Blue Kazoo with the upgrade is now rated to -5 deg F. The zippers work great and allow for the additional width of the upgrade bag. The combined weight of both bags is about 4.5 lbs."