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.
Ever before been on an overnight camping or backpacking journey yet didn't have a sleeping bag so you borrowed one from a close friend or a person you recognized? You crept right into that bag only to discover via the training course of the night that you either iced up to fatality due to the fact that you weren't cozy adequate or tossed as well as transformed because of pain or possibly also both.
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.