A dozen v.s. dozens of

INCORRECT		CORRECT
	There are a dozen of eggs on the table.		There are a dozen eggs on the table.

"Dozen" means twelve and therefore we do not use the proposition "of" with it. We never use "of" with exact number figures. We do, however, use "of" with the plural form to indicate that there are very many of them. For example, "Dozen of people showed up to listen to him speak."

The same is true for the plural form of other numbers, for example, "hundreds of", "thousands of", "millions of", etc.