11 Stocks Moving In Wednesday's After-Hours Session

Gainers

• Buffalo Wild Wings BWLD gained more than 20 percent. Even though sales of $496.7 million came in below estimates of $501.6 million, a raise in the earnings outlook for the full year drove the stock higher.
• Sarepta Therapeutics Inc SRPT traded up 4.2 percent after reporting a third-quarter net loss of 20 cents per share, 65 cents smaller than anticipated, on revenue of $46 million, which came in $5.23 million above estimates.
• Las Vegas Sands Corp. LVS moved up 1.8 percent on a top and bottom line beat for its third quarter. EPS of 77 cents beat estimates, while revenue of $3.2 billion came in $50 ahead of expectations.
• Tractor Supply Company TSCO spiked 1.85 percent on a double beat. Third quarter EPS beat by 4 cents, while revenue of $1.72 billion was $40 million larger than anticipated.

Losers

• Amgen, Inc. AMGN traded down 2.5 percent, even though third-quarter EPS of $3.27 and revenue of $5.77 billion beat estimates by 16 cents and $10 million respectively, as sales of Repatha, Krypolis, Aranesp, Prolia and Xgeva fell short of expectations.
• F5 Networks, Inc. FFIV lost a mere 1 percent on poor guidance. While Q4 EPS of $2.44 beat estimates, and revenue of $537.99 million beat by $3.28 million, revenue guidance for the first quarter was lower than expected.
• ServiceNow Inc NOW slipped more than 6 percent, even though revenue and guidance came in above expectations. Revenue of $491.5 was in line with estimates.
• Citrix Systems, Inc. CTXS lost almost 3 percent after reporting third-quarter EPS of $1.22, 18 cents above consensus, and revenue of $690.93 million, in line with expectations.
• Xilinx, Inc. XLNX shed 5.25 percent after a revenue miss. While second-quarter EPS beats estimates by 2 cents, revenue of $619.5 million missed them by $1.45 million.
• Ultra Clean Holdings Inc UCTT was down more than 10 percent on a third-quarter earnings miss.
• O'Reilly Automotive Inc ORLY lost almost 7 percent, driven by lukewarm third-quarter results. EPS of $3.22 beat estimates, but revenue of $2.34 billion was just in line with expectations.

After-hours price action occurs in an environment where fewer traders are participating in price discovery. Amid this lack of activity and liquidity in certain stocks, experienced traders will sometimes attempt to manipulate sentiment by placing an order at a price markedly different than a stock's closing price or last price.

It's conceivable less savvy investors could see this price action, assume the sharply higher or lower indication is a signal of news, buy or sell the stock, and ask questions later. This is one reason after-hours price action can sometimes evaporate by the next day's morning trading session (i.e. there is no news -- just trading activity).