I know this mug from the hospital. They are for newborns verwndet that not getting enough breast milk from their mums and should receive no Saugbverwirrung. The little glass is filled with a few ml debut milk and slightly inclined held at Babies lower lip so that some milk comes to the lower lip. The baby lick like little kittens automatically the milk from ... until then it works even with Mama. So is intended to bridge for the very young.