It combines the best of both. A warm sleeping bag is great, but it doesn’t help that much from the rain and whatever else might be flying around, like bugs. A tent, while nice, is just another thing to pack when you want to go camping light, and you have to set it up, take it down, and sometimes find the best place to put it.
This sleeping bag is interesting. It’s called a bivy bag. This one is the Observer Plus bivy bag, but there are a lot of these.
From the manufacturer: “The perfect sniper bivy bag with self-standing double pole support. Two tent poles form a small dome at the head end which provides enough space for the user to handle a rifle or other piece of equipment. The bivy bag slopes down from the shoulder to the foot end thus preventing straight lines which are easily spotted.
“The L-shaped opening makes it convenient to get in and out of the bag which can be closed with 2 zippers. All zippers are protected by a specially designed storm flap to make them absolutely waterproof. The big observation opening at the front allows an observation range of 180° and can be closed completely in bad weather. The user’s rifle and telescope can nevertheless still be placed in position through an observation slit.
“Both the observation opening and the access opening are fitted with a mosquito net. There are 5 loops on the back of the Observer to hold the insulating mat in place.”