McDonald's announced Monday that its popular but hard-to-find McRib sandwich will return to participating restaurants through November 14, 2011.

The 500-calorie, 26-grams of fat pork sandwich topped with slivered onions, sliced dill pickles and a signature barbeque sauce, is frequently available only when some restaurants want to make it.

It has even inspired an enthusiastic online fan base and a "McRib Locator" with several requests for its return.

"At this time, we can't speculate on its return in the future but we hope McRib fans will enjoy it now while it lasts," said McDonald's in a press release Monday.

It was first introduced in 2010 and sparked a 4.8 percent U.S. sales increase in November last year, according a company statement.

McRib without bones?

Some nutrition experts have critisized the fact that the pork is boneless.

"Doesn't the word 'rib' mean anything? If there is no rib, why hasn't the FTC taken an interest in this question," author of "In Defense of Food" book Michael Pollan told CBS News.