Berkshire Hathaway has built up sizable investments in a handful of companies, according to a filing released on Thursday.

Warren Buffett's modus operandi is to wait for price dislocations to present themselves. In a historically pricey stock market, locating value has been virtually impossible. Yet, with UnitedHealth Group stock losing more than half its value since the midpoint of April, a rare price dislocation has emerged.

In May, a 13F filing revealed that Berkshire Hathaway was buying mystery stocks. Now, at last, we know what they are.