Check out which companies are making headlines before the bell:
General Electric—Activist hedge fund Trian has taken a $2.5 billion stake in GE, the largest in the fund's history. GE said it welcomes Trian's involvement, while Trian said GE is in the midst of a bold transformation that should enhance shareholder value.
FireEye—Piper Jaffray downgraded the cyber security company's shares to "neutral" from "overweight," citing increasing competition and other factors.
Tesla—The electric carmaker reported deliveries of 11,580 vehicles during the third quarter, 49 percent more than a year earlier. That gives Tesla sales of just over 33,000 vehicles for the first nine months of the year, meaning that it could need a major push to reach its goal of 50,000 to 55,000 vehicle sales for 2015.
Vimpelcom—Norway's Telenor wants to sell its 33 percent stake in the Russian telecom company, with that Vimpelcom facing a bribery investigation by regulators in the U.S. and in the Netherlands.
Applied Materials—RBC downgraded the semiconductor equipment maker's stock to "underperform" from "sector perform," pointing to an overall drop in capital spending in the industry as well as what it considers an overly optimistic outlook by the company.
Toll Brothers—The luxury home builder was upgraded to "positive" from "neutral" at Susquehanna, saying current valuation and estimates don't accurately reflect Toll's potential 2016 results.