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 Polypore International (NYSE: PPO) were charged up today, gaining as much as 19% after the company reported fourth-quarter earnings.

So what: The company, which supplies its high-tech filtration products to battery makers, announced fourth-quarter results after the close yesterday. Revenue was up 12% from last year, to $170 million, while adjusted earnings per share rose 17% to $0.42. Wall Street was looking for $160 million and $0.34, respectively, for sales and EPS.

Now what: While the company didn't provide specific earnings guidance, management certainly made it sound like growth will continue. The company has been making significant investments in capacity expansion over the past year to meet, as CEO Robert Toth put it, "rapidly growing customer demand." Sounds good to me. Of course, with the stock currently trading at 34 times estimated 2011 earnings, high expectations are apparently already a part of the Polypore investors' playbook.

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Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.