A bivvy bag (also called bivi bag) can be described as a tent-like bag. It is basically just a waterproof bag that you and your sleeping bag would slot into. ) Bivvy bags are often constructed using lightweight waterproof material (usually a nylon), with a breathable top.

One of the things to be aware of is that while some bivvy bags will position themselves as being breathable, it can be difficult to have a fully breathable and fully waterproof bag.

Some bivvy bags are supplied with a small pole that creates a small open tent-like area around your body. This is handy because most bivvy bags create some condensation while you sleep. This happens because your body generates heat when you sleep at night and there is nowhere for the resulting vapour to go.

A bivvy bag is basically a waterproof cover for your sleeping bag. The good thing is a bivi bag is the perfect item to have with you if you plan on going camping without a tent.

It does not just keep your sleeping bag dry when out in the elements, but it also helps protect your food from animals and pests.