According to a filing with the SEC, Jeffrey Smith's Starboard Value now owns 4.2 million shares of Regis Corporation (NYSE: RGS ), giving it almost 7% of the total shares outstanding. The fund had reported owning 2.8 million shares at the end of September, making it one of the five largest single stock holdings by market value in Starboard's 13F portfolio (see more of Starboard's stock picks). Regis is a $960 million market cap company which operates and franchises hair salons with a focus on the United States. Its brands include Supercuts and MasterCuts as well as Regis Salons itself; the company generates about 20% of its revenue from in-location product sales. Starboard is an activist investor, most notable these days for its position in Office Depot Inc (NYSE: ODP ).