BERKELEY — Beer collaborations are nothing new, but the results are almost always worth a taste; a unique, one-off beer that shows off the qualities of both breweries. That’s exactly what Berkeley brewery, The Rare Barrel, and Colorado-based brewing giant, New Belgium Brewing, are set to release this week.

“Err on the Side of Awesome” is a sour beer collaboration from the two breweries; a blend of a cherry sour and two pale sours from aged barrels. Alex Wallash, co-owner of The Rare Barrel, describes the flavor profile as “assertively sour with bright notes of cherries, pineapple, [and] white wine…” The beer is slated to be released on tap tonight at The Rare Barrel’s Berkeley taproom.

Sour aficionados will find a special nugget in the cherry sour portion of the blend: it was aged in New Belgium’s pH1 barrel — one of New Belgium’s original seven oak barrels, and up until a year ago, kept by Russian River Brewing and featured in its Beatification beer. The pH1 barrel’s reputation of being the perfect blend of yeast and bacteria was even the inspiration for the name, The Rare Barrel.

New Belgium specialty brand manager and wood cellar blender, Lauren Salazar, received the pH1 barrel back from Russian River a year ago, loaded a cherry sour into it, and recently brought it out to use for a beer blend.

Wallash, Salazar and The Rare Barrel co-owner Jay Goodwin worked together to choose blends that would work well with the pH1 batch, settling on two pale sours to join together for the final Err on the Side of Awesome blend.

“We went into this collaboration with such mutual respect and friendship and the desire for this to be FUN,” said Salazar. “It developed as we talked about it — ph1, the barrel and the story really brought the whole thing to life.”

Err on the Side of Awesome is slated to debut at The Rare Barrel at 7 p.m. tonight, alongside other New Belgium beers on tap as well. In addition to The Rare Barrel, Salazar says the beer will be available at the following locations:

• City Beer Store, San Francisco, Sept. 18

• Toronado, San Francisco

• Hops & Hominy, San Francisco

• Church Key, San Francisco

• Fat Angel, San Francisco

• Dirty Water, San Francisco

• Three Sheets, Dublin

• The Hop Grenade, Concord, Sept. 18

• Beer Baron, Livermore

• The Growler, Danville

• Ramen Shop, Oakland, Sept. 20

• Beer Revolution, Oakland, next week

• Albany Taproom, Albany, Oct. 8

• ØL Beercafe & Bottleshop, Walnut Creek, Sept. 26