A survival blanket weighs little (there are models of 50 grams) costs little more than a beer rod, and serves many purposes. Among its multiple uses is sheltering you in an unforeseen bivouac (main reason to take it), shelter from rain or isolate you from the wet soil in a bivouac (provided in this case), or to rest sheltered from the sun in summer in those mountains in those that do not find a shadow.
In the market there are many models of different brands, but by their shape we can divide them into 2 groups.
On the one hand traditional blankets, rectangular in shape, of different sizes, with more possibilities of use to isolate us from the ground or as shelter from the rain. And on the other hand those manufactured in the form of a bag or cover, which will protect us better in the case of an unforeseen bivouac.
As for the materials used, basically consist of a base of some plastic material (polyester or polyethylene normally), more or less fine, on which metallic layers are deposited in order to reflect the heat of our body. In some models, one of the faces has an orange color to facilitate the location of the user in the case of a rescue.
Here we have to have one thing clear. This type of blankets barely isolates as such, it is not like a sleeping bag filled with an insulator (fiber or feather) that retains layers of air. The only thing it does is reflect the heat that our body gives off.
Lighter blankets are thinner, usually cheaper, and sometimes smaller. As an advantage they have that we will not be too lazy to always carry it in the backpack, although it is usual that they do not survive more than one night of use. Before buying it, check that it is the right size, or you can take an unpleasant surprise when it is most needed.
There are thicker and sturdier blankets that will last you longer, although you should know that once opened, you will almost never get to fold it again and that it will occupy the same. Some models have a small carrying case that will make it much easier for them to keep it little more than new.
Once these concepts are clarified, we can give a review of some of the products that we can find in the market, being clear that there are more models and manufacturers than those exposed here.
In the catalog of some of the usual mountain material manufacturers in the stores of our country we have models of simple survival blankets, as in the case of Ferrino , Salewa and Vaude(bottom image), with weights between 55 grams of Ferrino and 60 grams of Salewa and Vaude. In this case, the weight is not due to differences in thickness of the material but to the size, since in the case of Vaude and Salewa they measure of the order of 210/220 cm long by 160 cm wide, the Ferrino only has 130 cm wide (130 cm wide are enough to cover, but to “wrap” is a bit fair). The prices of these types of blankets oscillate in general between 4 and 7 € approximately.