To be installed on the front if you are only putting on two, mostly for the steering. I have used them in the past, although on a Geo Tracker not a Subaru. I have to say they are supposed to be for emergency use only and only in snow or ice. On dry road it will destroy the coils I think. Also, top speed is pretty low. They do work but if you try and go too fast I think your fillings will fall out
I have a friend that had good things to say about these tire socks that go over the tires for snow but honestly I haven't used them myself.
I got the SC1036 for my 18-inch Sport tires. Don't actually use it since our AWD and OEM tires cover most of the snow requirements in California except in extreme circumstances. Just keeping it in the trunk for legal compliance.
My family and I live in Wisconsin. We switch to winter tires that are mounted on steel wheels. We love the way the car handles on ice and snow. The all season tires on the alloy rims don't get damaged by the salt and we are able to go anywhere we need to. We switch back and forth when Temps are consistantly above or below 45 F.
I remember years ago that Washington state used to have a 'chain law' that permitted vehicles with AWD to proceed without tire chains, which often resulted in many Jeeps with pavement tires spinning off into the ditch.
I used to drive a tractor-trailer, and I LOATHED having to hang iron on my tires. Of course, truck chains can weigh 20 lbs or more each, but having to get out in the cold rain to install them on a mountain grade is something that I tried to avoid as much as possible, even to the extent that it was preferable to just wait-out the storm.
Having learned to drive in the great lakes snowbelt, I've had an enormous amount of experience driving on snow and ice. As a result, unless chains were explicitly required I never used them. Where I live now, we get some 100-150" of snowfall each winter, but I haven't seen one person use tire chains here in 30 years (except for once on a farm tractor pulling a pickup out of a ditch..).
I also lived where we got 120+" of snow per year. I've had to use the tire cables once in my my life to get to work due to a emergency during a huge storm. Honestly with a good set of snows, the Subaru AWD system is pretty good. Short of High Centering, which I've done a number of times messing around, I think having tire cables in the car will mostly just make you feel good.
To Alex's point if you do have cables and honestly think you are going to need or use them. Don't wait until you are somewhere outside in crappy conditions to figure out how to properly install them. Do a practice run in your warm dry garage. It's harder than you think under the best of conditions let alone when it's hard to feel you fingers
Tire tec has come a long way with the new rubber compounds. Chains aren't as necessary as they once were for most people. I think a good set of quality snows and a shovel, for when you high center are your best bet.