First came boneless wings. Now KFC wants you to chow down on a sandwich that uses (what else?) chicken for the bun.

The KFC Double Down, which launches Monday, is essentially a sandwich with two chicken filets taking the place of bread slices. In between are two pieces of bacon, melted slices of Monterey Jack and Pepper Jack cheese and a zesty sauce.

How much will it cost? About $5 and 540 calories (460 for the grilled version), putting it on caloric par with fast-food standards like the McDonald’s Big Mac or a large order of french fries at Burger King.

But calories aren’t everything. Nutritionists caution that consumers also should pay attention to the sandwich’s salt and fat.

The Double Down has 1,380 milligrams of sodium (1,430 milligrams grilled). That’s close to the American Heart Association’s recommendation that adults eat less than 1,500 milligrams of sodium per day.

“This is not a healthy choice,” said Walter Willett, chairman of the nutrition department at the Harvard School of Public Health.