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 laser manufacturer Rofin-Sinar Technologies (Nasdaq: RSTI) fell more than 11% after the company guided to Q1 revenue and earnings targets that were well below Wall Street's estimates.

So what: Management cited a "cautious sentiment" among industrial customers in projecting $137 to $142 million in revenue and $0.33 to $0.36 in earnings per share. Analysts had been calling for $0.50 a share of profit on $153.7 million in revenue, according to data compiled by Yahoo! Finance.

Now what: Rofin-Sinar's poor guidance overshadowed what was an otherwise good Q4. Earnings came in $0.05 ahead of estimates while revenue grew 36% year over year. Do you think the sell-off was premature? Would you buy shares at current prices? Please weigh in using the comments box below.

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Fool contributor Tim Beyers is a member of the Motley Fool Rule Breakers stock-picking team. He didn't own shares in any of the companies mentioned in this article at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Google+ or Twitter, where he goes by @milehighfool. You can also get his insights delivered directly to your RSS reader.

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