Data storage specialist SanDisk (UNKNOWN:SNDK.DL) just reported results for the fourth quarter of 2013.

SanDisk's $1.71 of adjusted earnings per share easily surpassed the $1.57 Wall Street target. On the top line, SanDisk met expectations exactly with $1.7 billion in total revenue. That's a 63% year-over-year earnings boost on the back of 12% higher sales.

In the earnings call, SanDisk set revenue guidance for the first quarter just below analyst expectations.

Reacting to SanDisk's solid fourth quarter and the ensuing soft revenue guidance, investors took the stock for a ride. SanDisk shares traded up 3.1% in after-hours action, then down 3.9% from closing prices, and finally came to rest close to the afternoon's closing levels.

To explain the quarter's steady performance, CEO Sanjay Mehrotra pointed to strong execution and favorable shifts in the company's product mix. "Our SSD product revenue set another quarterly record and represented 19 percent of our annual revenue," he said, "and we also set a record for annual retail product revenue."

These product lines tend to sell at higher margins than commodity storage and shipments to OEM partners. SanDisk reported gross margins at 50.7% this quarter, a strong bounce back from the 39.8% gross margins seen a year ago.