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Size matters.

Subway customers wont need a tape measure to be sure their 12-inch torpedo

It’s National Sandwich Day, and Subway is rewarding customers with a free sandwich to celebrate.

Subway customers who by any sub and a 30-ounce fountain drink will get one sub for free as part of the “Buy One, Give One” offer at participating locations.

CNN reports that the sandwich was popularized in the 1700s in England by John Montagu, the fourth Earl of Sandwich. He ordered beef between slices of bread so he could play cards and eat at the same time.

Market research firm Datassential surveyed Americans on their favorite types of sandwiches. The winner was turkey, followed by ham and chicken.

The survey also said when Americans go out to eat, they are more likely to order subs or cheese steak sandwiches.

At home, though, a good old peanut butter and jelly or grilled cheese is good enough to hit the spot.

What is your favorite type of sandwich? Vote in our poll below!

Read more here.