No insulation. Water proof rubbery material on the bottom 4" or so. Water resistant very thightly woven materian on the upper part.

When stomping about in snow, basically any bag you pull over your boot will keep you substantially warmer - insulated or not.

Don't underestimate the cooling effect of snow on boots! Melting snow will drain heat from your foot. Snow will stick to your boot and find its way between the laces. And unless your boot is very water proof you will get wet. Most skiing boots and many trecking boots are not anywhere water proof enough for prolonged stomping in the snow.

The benefits of these is that they pack relatively small, are water proof on the lowest part and very water resistant on the upper part. I can't vouch for the durability (yet), but I know plenty of people who owns a pair of these and no complaints so far.

It is also very easy to improvise some insulation for these foot sacks. Carve out a sole from an old cell foam ground pad. Or cut out and stitch together something from an old fleece blanket or sweather. That way you can also use these as "camp boots".