Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
They are the same magnetic adapter but the 15" is larger and supplies more watts.
They are interchangeable but I would be careful using the airs 45w adapter on a 15" retina. I often use a 60w adapter from my 13" pro on my 15" pro
 
They are the same magnetic adapter but the 15" is larger and supplies more watts.
They are interchangeable but I would be careful using the airs 45w adapter on a 15" retina. I often use a 60w adapter from my 13" pro on my 15" pro

It doesn't matter which one you use with which computer because the computer sets the amount of power it draws not the adapter.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.