Wine barrels are most commonly made from oak wood, specifically from the species Quercus alba, Quercus robur, and Quercus petraea. Oak is preferred for wine barrel making because it has a tight grain structure, which allows for good flavor penetration and maintains the integrity of the barrel. Additionally, oak imparts desirable flavors and aromas to wine, such as vanilla, spice, and toast, as well as aiding in the aging process.