Benzinga's After Hours Gainers (ABK, BJ, SUN, COWN)

Among the stocks that are moving in the after hours this evening are Ambac Financial (NYSE: ABK), BJ's Wholesale Club (NYSE: BJ), Sunoco (NYSE: SUN), and Cowen & Co. (NASDAQ: COWN).

During the regular trading session, shares of Ambac Financial (ABK) gained an incredible 104%, closing at $2.25. The company reported that they had swung to a profit on Friday, when the stock gained 70%. Tonight, in the after hours the stock has tacked on an additional 10% and is now trading hands for $2.48.

Shares of BJ's Wholesale Club (BJ) are more than making up for today's 1.64% loss during regular trading hours with a gain of 2.21% in the after hours. There does not appear to be any news driving the activity in the name.

Sunoco (SUN) has moved 2.15% higher in the after hours trading session, after falling 1.53% during normal market hours. This is one of a number of energy related names that are seeing some buying pressure in the late trading session.

Boutique investment bank, Cowen & Co. (COWN) has jumped 8.6% in the late session, after losing 2.56% during normal market hours. There does not appear to be any news driving trading in this stock. Keep an eye on this name in the pre-market and at the opening bell tomorrow morning. COWN is a small cap name and there is the potential for news or rumors to create volatility in tomorrow's session.