The tequila in this lot was double-distilled in copper double-column stills from agave plants primarily harvested in 1984 and stored in barrels in early 1994, ten years after harvest. The barrels were aged for an additional 11 years in a cooler, highland location after spending a decade in a dry, earthen-floor room in Atotonilco el Alto.

Most of the barrels used to age the tequila were previously used for California white wine, while one barrel had previously held Canadian rye whiskey. Master distiller Enrique Fonseca created this tequila with the aim of producing the world's longest-aged tequila.

Unlike other releases in the 2015 line, which incorporated pot still tequila, the 21 year old in this lot was exclusively produced using copper double-column stills. The majority of the tequila was aged in barrels that previously held Canadian rye whiskey, with only one barrel having previously held California white wine. The barrels spent a total of 21 years aging in two different locations.