The grape varieties used to make Tokaji wines are Furmint, Harslevelu and Sárga Muskotály (Muscat Blanc), in that order of importance. Furmint, which dominates the Tokaji blend, is renowned for its naturally high acidity, high sugar levels and spicy aromatic profile. The first two of these characteristics are responsible for the wine's phenomenal ageing potential, while the latter provides a flavor distinct from any other sweet wine. The aszú (botrytized) wines for which Tokaj is known are made from grapes affected by benevolent Botrytis cinerea fungus. This beneficial fungus dehydrates the grape berries, concentrating their sugars and leaving a trademark honeysuckle aroma in the wine. The sweetness of Tokaji aszu wines is indicated in "puttonyos". A puttonyo is a large basket used for harvesting grapes; the number of puttonyos of aszu grapes added to a 136-liter barrel of base wine was a traditional measure of the wines' sweetness. In modern times this has been transposed into a more precise system based on grams per liter of residual sugar. Three puttonyos indicates 25g/l - the lowest sugar content and thus the least sweet of the aszu wine styles. Each additional puttonyo thereafter indicates an increase of 5g/l of residual sugar. Eszencia is the very sweetest aszu style. With around 800 g/l of residual sugar, it is so sweet, and so low in alcohol (about 5 percent ABV) that it hardly qualifies as wine at all. It is the undiluted, barely fermented juice of botrytized berries. Unsurprisingly, Eszencia is one of the rarest and most expensive wines on earth.