Whistlepig is a relatively new entrant on the American WHISKEY scene _ and one that is gaining in popularity.The 100% rye WHISKEY that makes up the core Whistlepig 10 Year Old is barreled and matured initially by Alberta Distillers in Canada before being shipped to Vermont for re-barreling and additional aging in Whistlepigs hands. This is the main difference from Mastersons which I believe just bottles the Alberta WHISKEY straight from the Canadian barrels. Whistlepig 10 yo was created by Dave Pickerell the former Master Distiller of Makers Mark.This is an unmalted rye as Alberta Distillers has developed its own proprietary enzymes for converting rye starch into sugar. In order to meet American standards for a straight rye the source Canadian WHISKEY for Whistlepig must have been distilled to an alcohol content of 80% or less (thus keeping a higher proportion of congeners than most Canadian whiskies which can be distilled higher). It must also have entered into virgin charred oak barrels for aging (which is relatively less common here). The end result is a more flavourful experience than most Canadian rye whiskies. Note these aspects are equally true for the Mastersons 10 Year Old Straight Rye which I recently reviewed.