Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of plastic container maker Graham Packaging (NYSE: GRM) soared more than 26% today after larger rival Silgan Holdings (Nasdaq: SLGN) agreed to buy the company for about $4.1 billion, including debt.

So what: The deal -- in which Graham shareholders will receive 0.402 of Silgan shares and $4.75 for each share owned -- values Graham at about $19.56 per share and represents a 17% premium to its Tuesday close. Silgan is making the move to expand its range of offerings, and judging by the stock's 13% pop today, Mr. Market seems quite pleased with the strategy.

Now what: While Graham's upside is now limited, Silgan might be a long-term investment worth owning. In fact, Silgan said it expects the deal to generate about $500 million in free cash flow, be accretive to earnings after one year, and slash operating costs by roughly $50 million by the third year. Of course, given the fact that Silgan will assume quite a bit of debt with the deal, the stock might be more appropriate for less risk-averse investors.

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