Half beer + half grapefruit soda = total surprise.

That’s what the folks at Marietta’s Red Hare Brewing quickly figured out when they released their SPF 50/50 beer into the market last March and couldn’t keep up with demand.

“It was an incredible juggernaut of a brand,” said Chris Green, vice president and general manager of the 1998 Delk Industrial Blvd. brewery.

The brewery is having a party next Saturday to relaunch its beloved craft beer concoction for good into the market.

So what is this business with this bionic brew?

Green said the idea came about after their founder Roger Davis took a trip to Europe, where he sampled many of the traditional blended beer mixtures — usually a lager and lemonade.

Those traditional amalgams are called a radler or a shandy.

Davis brought all those ideas and (maybe cloudy) memories of the beer back and began tinkering.

They landed on a combo of their Gangway IPA and a grapefruit soda made at the brewery with pure cane sugar and named the half-and-half result SPF 50/50.

“For people who enjoy IPAs, you get a lot of hop flavor, but … the grapefruit soda balances it out,” is how Green described the radler.

(For beer nerds: It’s 4.2 percent ABV with 38 IBU.)

He said they sold as much SPF by volume in five months as they sold of their mainstay lager and IPA, individually, all of last year.

The SPF took home a gold medal in the "Out of Bounds Pale Ale" category of the 2016 U.S. Open Beer Championship.

“For the first two months, we couldn’t make enough,” Green said. “Production was all we could do to keep up.

Now they are excited to re-release the beer March 25, this time in a 16-ounce can.

That party is from 2 to 6 p.m. with live music and a food truck serving up Cajun fare. It's $12 for a tour, which comes with a tasting and a souvenir SPF glass. For $8 more, you get a six-pack of the stuff to take home.

It’s $5 for non-drinkers and children, which buys a pint glass, brewery tour and 36 ounces of their homemade root beer and grapefruit soda.