If you're new to the category of extra brut, it technically refers to the level of dosage (sugar addition) to the final blend, being very low. This normally sits between 0-6 grams per litre (g/L) and the two wines sit at 2 g/L.
Dosage is just one aspect. It also features longer ageing in the cellars (typically 3-5 years) and use of excellent quality fruit that has ripened perfectly. Ripeness in the fruit means that there is no need to add much 'dosage' as they have achieved it in the vineyards through biological means.
The makers of this wine are focused on revealing the natural qualities of the fruit, allowing it to shine through without "covering it" with any sugar.
