Answer: They beep when they back up.

	Post-Gazette A chicken burrito-to-be travels down an assembly line, where it is stuffed with a choice of fillings. Click photo for larger image.

Question: How big is a burrito from Chipotle Mexican Grill?

The burrito, Chipotle's signature creation, is a huge, aluminum-foil-wrapped bundle that is 7 inches long, has a 9 1/2-inch circumference and weighs 1 pound 3 ounces. Or more.

It's fun to watch one being made.

A special steamer saturates the tortilla with moisture and heat, which makes it pliable enough to roll up so it won't burst when stretched. The burrito begins when the warm flour tortilla is placed on a large piece of aluminum foil. (Corn tortillas don't work because they aren't as big or flexible.) The foil is essential as a structural support to ensure that the burrito doesn't rupture like a haggis while it's being eaten.

Once the tortilla is in place, the burrito-to-be travels down an assembly line. Depending on what is ordered, three or four servers move the tortilla along the mise en place to add, say, a spoon of cilantro-lime rice, a choice of pinto or vegetarian black beans, and a choice of 4 ounces of protein -- chipotle pepper-adobo grilled chicken, braised, hand-pulled pork carnitas, spicy shredded beef barbacoa or marinated steak. It can be customized further with a choice of four salsas, cheese, guacamole or sour cream or all of the above.

At the last station, the tortilla is folded, tightened and foil-wrapped into a firm package.

Give or take the extras, you'll pay something like $6 or $7.

Take any combination of ingredients and have them your way, with or without the giant tortilla:

Let's say you are a vegetarian. Choose the beans, cheese, guacamole and sauteed peppers and onions for a veggie fajita.

Vegan? Beans, guacamole, peppers and onions with roasted chili-corn salsa and chips.

Kids? Crispy corn tacos with chicken. Or cheese quesadillas. Just ask.

Atkins diet? Big bowl of chilled romaine, topped with carnitas and chicken, a couple of salsas, sour cream and guac.

Carry out? Compose a swell dinner at home when you order components packed separately.

Note to sticklers: Chipotle acknowledges that its burrito was inspired by and is a descendent of the aluminum-foil wrapped San Francisco burrito, born in the 1960s in that city's taquerias in the Mission District, where it is still served. The San Francisco burrito is also the forerunner of the ubiquitous "wrap" served in just about every casual restaurant. A wrap involves placing a tortilla-like "wrapper" around just about any combination of food. A wrap may contain burrito ingredients, but a burrito is not a wrap.