From the maker:

Stranahan’s Sherry Cask is our latest innovation & expression in single malt. We take our four-year-old Rocky Mountain Single Malt and then transfer it to 500-liter Oloroso Sherry Barrels to cask finish. Procured from the Andalusia region of southern Spain, these sherry barrels have been aging wine for over 40 years, leaving a depth of flavor soaked into the ancient oak staves.