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 industrial supplier Fastenal (Nasdaq: FAST) have fallen 10% today after the company reported May sales.

So what: During the month of May, sales rose 18.4% to $275 million but analysts had set their sights even higher. To meet estimates of $824 million in sales for the quarter, June sales will have to be $288 million, a high bar after one of the best months of the year fell short.

Now what: Before we go freaking out, let's put these numbers into perspective. Stores open at least two years increased sales 10.1% in May and daily sales grew 13.1% (because of an extra sales day versus last year). The company is performing very well, but the stock may have gotten ahead of itself. Shares are trading at 22 times forward earnings, a lofty valuation for a retailer like this. I wouldn't buy the dip but let's not take today's fall to mean that Fastenal is in any sort of trouble at the moment.

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