To extend my 40 degree down bag (really nice bag, but I just don't have the cash to buy new "nice" bags for each temp range) with either/and liner, and a poncho liner (from my Army days). The poncho liner serves multiple purposes for both the trail and car camping. It's a nice, versatile implement. Used alone in summer it makes a good loose throw for cool evenings. I like the fact that it is big enough to fold over into a complete sleeping bag.