What size eggs do you normally buy? I usually get large or extra large. I recently found out that the standard size here in the U.S. is LARGE.
It's very rare when I come across a recipe that actually specifies egg size so I always wonder if I'm using the right size egg. Since the standard is large that means when you're making a recipe that calls for an egg but doesn't say what size, large is the safest bet. Of course if the recipe does specify egg size you should do what it says.