The temperature a sleeping bag is rated for is the bare minimum temperature at which it will keep you alive, but you will be far from comfortable. The rule of thumb is to get a bag that is rated at least ten degrees lower than the lowest temperature in which you expect to use it. But the caveat, once you hit that 10 degree buffer zone you will definitely need to add more layers.

Kelty specifies that their temp ratings specify that the user be sleeping on a 1" pad and wearing base layer, hat and socks, which is how sleeping bags are normally used.

It's there for everybody to read.

The Light Year is an excellant bag.

is it really the size of a soccer ball? or did you mean soft ball. does anydoby know how small this stuffs to?