The traditional veladora is glass. It has a circular base that slightly opens up as the outer surface extends to the mouth. The shape of the mouth allows the mezcal to “breathe”. Additionally, because its wide mouth, when someone takes a sip of mezcal from a veladora, there’s little risk of the strong alcohol fumes overwhelming them.
The veladora is convenient as well. The ribbed outer surface makes it easy to grip, and its shape makes accidentally breaking one fairly difficult. It’s also compact enough to travel with.
Originally these glass cups were used in Catholic churches to contain prayer candles. . Each vaso has a cruxifix imprinted on its base to remind you of its purpose. Someone had the great idea of borrowing the candle container from church to drink mezcal and a whole new category was born. Today you find them both in churches and bars in Mexico.