What is Berkshire Hathaway class b stock?

Berkshire Hathaway has two classes of common stock. Class A shares and class B shares. A class B share represents 1/1,500 the equity in the company as a class A share. Class A shares can be converted to class B shares at any time, but class B shares only carry 1/10,000 the voting rights of a class A share. Please see http://www.berkshirehathaway.com/compab.pdf for more details.