Bushmills 21 Year Old is a blend of single malts that are matured for a minimum of 19 years in hand-picked Oloroso and Bourbon casks and then finished in Madeira casks for a further two years. This unusually long finishing period allows the single malt to mature patiently and take on deeper notes of ripe fruit and dried raisins from the fortified Portuguese wine casks. This whisky is only made in limited quantities and each bottle is numbered.