According to Berkshire's most recent filing, which is as of June 30, it has bought approximately 5 million shares of UnitedHealth Group. It's a notable position for Berkshire, but it's not a huge one -- UnitedHealth accounts for just 0.5% of its total portfolio.

UnitedHealth Group shares popped Friday after Berkshire Hathaway announced it purchased 5 million shares of the insurance giant.

Beaten-down UNH is set to challenge its 50-day moving average after a major vote of confidence from the Oracle of Omaha.