Where is the old full size options for images?

Remember when you had an image that was too big, and when you chose the full size option, it will automatically scale it for you so that it would fit right into the posting area dimensions. Where is that option now or how can I get it?

(If you don’t know what I’m talking about, say the posting area is 500px in width and you had a 550*300 image. It would scale it so that the width is 500px and fit right in.)