2 much better than none, but be aware your rear tyres, will in comparision, have much less grip than your front, making your car prone to rear end sliding if you're not careful. I have 2, but if I had the funds I would buy 4, especially if you were going to be doing a lot of driving. If you shop around you should be able to get them for approx €75 ea. fitted. Socks are a great "get you home on the back roads" option, but for day to day driving, you can't beat the winter tyres.