Shake Shack is an upscale eatery where customers can enjoy satisfying burgers for a premium price. It's also now a publicly traded company with a quickly rising stock price.

Shake Shack released an initial public offering (IPO) price of $21 per share Thursday night. Friday, its shares (SHAK) hit as high as $50 a share. In midday trading the stock is still at $48.67 (up over 130 percent).

Shake Shack is a fast-casual restaurant, similar to Chipotle or Five Guys. These types of restaurants give customers the convenience of a fast food restaurant but the comfort of knowing better ingredients and cooking methods are used.

The company is still relatively small with only 63 locations worldwide. That could be changing though. Shake Shack plans to open at least 10 company-owned locations in the U.S. each fiscal year.

Certainly, burgers are a popular item on menus. Last year, 9 billion burgers were ordered at U.S. restaurants and outlets, a 3 percent gain from 2013, according to data from NPD Group, The New York Times reported.

Danny Meyer started it all from a hot dog cart in Manhattan in 2001. Since then, he opened several other Manhattan locations close to each other. He was able to walk to each one to ensure guests were getting proper service.

Now, Meyer is not able to walk to every location he has, and with the expansion, he certainly will have to trust the restaurant employees to deliver the service he wants each guest to receive.

Only seven fast-casual restaurants have gone public in the last 10 years. If Shake Shack can maintain its gains today, the stock will be have the best first-day performance of all of those companies in that time period, according to Fortune.

What do you think of Shake Shack? Have you ever tried it? Leave us a comment below and let us know what you think.