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 Aeroflex Holding (NYSE: ARX) fell nearly 18% in early trading today after guiding to much lower fiscal-first-quarter revenue and earnings. The stock remained down more than 16% as the closing bell approached.

So what: Fourth-quarter adjusted earnings were OK, coming in at $0.35 a share -- a penny better than the consensus estimate, reported. Revenue, meanwhile, rose only 4.7% to $198.7 million. Wall Street had been calling for $199.3 million.

Now what: As big as that miss was, it was guidance that sent investors packing. Aeroflex, which specializes in sensitive electronics, expects $160 million to $165 million in Q1 revenue and $0.09 to $0.11 per share in adjusted earnings. Analysts were expecting a more robust $0.19 on $175.03 million in revenue. No wonder investors were bailing out. Where do you stand on this stock? Would you use the sell-off as a buying opportunity? Weigh in using the comments box below.

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