Tires: Tire specs, subaru outback, tire specs

Question
I need to replace a tire on my Subaru Outback due to a nail.  Because my tires are only a year old, I want to replace one and  not all four.  I have found the same tire online with the same specifications as the tires I have now with the exception that mine end in M+S (Mud & Snow) and the one online ends in BSW (black sidewall).  Does this indicate a different tread size?  Is it enough of a difference that I shouldn't buy only one and should succumb to buying 4 new tires?

Answer
Brooke,

As you found out. M+ S means "Mud and Snow" - an All Season.  BSW means "Black Sidewall".  So these are not in conflict.  My best guess is that they are the same.

But to be sure that replacing one tire is going to work, you need to measure the tread depth of the tires.  If they have less than are more than 6/32nds remaining, then replacing one tire runs the risk of ruining the drivetrain, so you should replace all 4.