That's ...mei Mass!
...mei Mass! ribbons are approx. 2 cm wide, slightly elastic ribbons that fit perfectly into the groove below the rim of the beer mug. The purpose of the ribbons: to avoid getting beer mugs mixed up in beer gardens, at the Oktoberfest or other folk festivals.
“...mei Mass!“ ribbons are a charming accessory to go with your mug and your traditional or trendy outfit. And a nice present for flirting, exchanging or collecting.