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 travel and business products specialist Tumi Holdings (NYSE:TUMI) plunged 11% today after its quarterly results and outlook missed Wall Street expectations.

So what: Tumi's second-quarter EPS of $0.18 was pretty much in line with estimates, but a wide miss on the top line -- revenue of $108.2 million versus the consensus of $114 million -- coupled with downbeat guidance for the full year reinforces concerns over slowing growth going forward. In fact, same-store sales increased just 4.6% compared to an 8% jump in the year-ago period, suggesting that its rivals are making some market share headway.

Now what: Management now sees full-year EPS of $0.76 to $0.82 on revenue growth of 16% to 18%, down from its prior view of $0.82 to $0.86 and 18% to 20%. "Looking out to the second half of the year, we have a strong pipeline of store openings in favorable markets," said CEO Jerome Griffith. "We continue to make strides in capitalizing on Tumi's global status as an iconic premium lifestyle brand, and we remain focused on, and confident in, our long-term growth opportunities in 2013 and beyond." Given its extra-volatile stock and shaky competitive position, however, Tumi might just have too much baggage to bet on those prospects.