Crooked Stave and Upslope Brewing collaborated on a sour ale. The base beer is the Belgian Style Pale Ale from Upslope that was inoculated with Brettanomyces and Lactobacillus which were carefully selected then were aged in first-time red wine barrels. Crook Stave’s head brewer/owner, Chad Yakobson and Alex Violette, Upslope Brewing’s head brewer hand selected the wine barrels from Rocky Mountain Barrel Co. The barrels were separated with each brewery aging them at their facility. With this in mind, the end result will be that the sour ales from the two breweries will have different qualities to them.
As of this writing there are plenty of cans of Feris Flexus from Upslope and bottles of it from Crooked Stave at local liquor stores. Don't know if you can still buy them at the taprooms.