Shares of Aramark /zigman2/quotes/204468030/composite ARMK +2.51% shot up 12% toward a 10-month high in premarket trading Monday, after hedge fund Mantle Ridge L.P. disclosed that it had taken a large equity stake in the food and uniform services company. In a 13D filing with the Securities and Exchange Commission late Friday, Mantle Ridge disclosed that it owned 24.1 million Aramark shares, or 9.8% of the shares outstanding. That would make Mantle Ridge the largest shareholder, according to FactSet data. Including cash-settled forward transactions and call options, Mantle Ridge sad it has "economic exposure" of a total of 49.3 million Aramark shares, or 20% of the shares outstanding. Mantle Ridge said in the 13D filing that it intends to have "conversations, meetings and other communications" with Aramark's board of directors, management and certain shareholders to discuss the company's business, strategies, governance and composition of the management team and board, regarding "possibilities" for changes. In a statement following the 13D, Aramark said it is "focused on maximizing long-term value for all of our shareholders, and welcomes open communication and constructive dialogue with our shareholders toward that goal." Stifel Nicolaus and Instinet both upgraded Aramark to buy on Monday. Aramark's stock has run up 28% year to date through Friday, while the S&P 500 /zigman2/quotes/210599714/realtime SPX +0.78% has gained 15%.