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 Graham Packaging (NYSE: GRM) surged more than 19% after a yet-to-be-identified third party bid $25 a share for the company. That's a 28% premium to the $4.1 billion bid Silgan Holdings (Nasdaq: SLGN) made in April.

So what: Investors cheered Silgan's planned acquisition of Graham Packaging at the time the deal was announced. Today, the stock has slumped as much as 7%. Shareholders see that much value in a combination with Graham.

Now what: The question now is whether Graham's board will back the new offer, and if so, whether Silgan would match or beat the new bid. I think both are likely. Graham is trading for a little less than 13 times next year's earnings, which are expected to improve 23%. Silgan could substantially up its offer and still get long-term value from a deal.

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