Sonic Corp. (SONC  ), parent company of drive-in fast food chain Sonic, is set to be acquired by Inspire Brands, Inc., in an agreement announced by both companies last week. The deal, valued at $2.3 billion including debt, is set to close by the end of the year and will see Inspire Brands, the parent company of fast food chain Arby's, take control of the US's fourth-largest hamburger chain.

Under the deal, Sonic will become a privately held subsidiary of Inspire Brands, which also owns Buffalo Wild Wings and Rusty Taco. Shareholders of Sonic will receive $43.50 per share in cash - an 18.8% premium compared to share value on September 24, 2018, the day before the deal's announcement. As news of the acquisition broke Tuesday, September 25, 2018, Sonic's stock rose more than 18%, with share prices reaching an all-time record of $44.87.

Famous for its retro atmosphere and memorable TV ad campaigns, Sonic serves classic American fast food, with offerings like hamburgers, hot dogs, french fries, and shakes. The '50s-style chain stands out from the competition because of its old-fashioned drive-in service, which allows customers to order and dine in their cars, and its rollerskating "carhops," who serve diners at their car windows.

"Sonic is a highly differentiated brand and is an ideal fit for the Inspire family," said Paul Brown, Chief Executive Officer of Inspire, in a press release. Formed in February of this year, the Atlanta-based Inspire Brands was created after the purchase of the sports bar franchise Buffalo Wild Wings by Arby's Restaurant Group, Inc. Backed by private-equity firm Roark Capital Group, which owns a majority in the company, Inspire Brands has sought to expand its portfolio of restaurants. With the acquisition of Sonic and its 3600 storefronts, the company will now boast combined annual sales of over $12 billion and more than 8000 company-owned and franchised locations.

Inspire's purchase of Sonic is in line with the company's recent acquisitions of diverse brands. "Up and down the spectrum, even in QSR, we would want the brands to be as complementary as possible," Brown said in a February interview with Business Insider. "You don't want brands that are right on top of each other. It's harder from an internal standpoint. You want to keep lines between the brands. If they get too close together, it gets harder to manage."