In 2013, Oud Beersel acquired 65 Demi-Muids to mature its lambic beers on. These are oak barrels of about 600 litres with thick staves, which are mainly used in the wine industry. For this special Oude Geuze, Oud Beersel selected its best Demi-Muids with Lambics that have matured for 1 to 4 years in these barrels. Because the staves allow less oxygen absorption than other small barrels, the Lambic on these barrels is more round and tender.