If you see a +20 degree score that would certainly indicate that the bag should be cozy enough for temperatures that are 20 levels or warmer.. And if you see a - 20 level score then it has actually been figured out that the bag needs to be cozy sufficient for minus 20 degree climate.
If you are in the mountains and also only plan to trek Fall, summer and spring, after that obtain a 3 season resting bag. (Example: claim that the average reduced in the mountains throughout the spring is 20 levels Fahrenheit, after that take away 20 degrees and look for a sleeping bag that's ranked at 0 degrees. Draft Collar: This is a tube at the base of the hood. It "closes" off the area at the neck so that air doesn't get away. When experimenting with a bag, see to it that this tube is comfortable.
The other sacrifice is the size or thickness of the bag. A mummy sleeping bag essentially will certainly be much smaller sized for bring around which is why it is a preference for many backpackers/hikers. The rectangular resting bag isn't as small yet because it's not common to be lugging it, apart from somewhere in a vehicle while getting to your intended location, the bulkiness of the bag is not as large a problem.