I bought the bottle warmer thanks to the positive ions Renz and can now say from personal experience that we are very satisfied! The processing of the hot water bottle is very good. The handling is super easy. The plastic container can be read, how much time it takes to warm up a glass (glass scale size / time). The glass is simply placed in the plastic container, water from the pot purely poured on it and cover. Short wait, while from time to stir and even the food is ready.
I especially appreciate that it is in the lid of the plastic container is a screw cap. Thus it can not happen, that water runs out of the backpack vacuum jug accidentally in the pocket /.
We tried times how long can we keep warm boiled water and are come to more than 12 hours..
The size of the bottle warmer in my opinion is perfectly fine. Even in a small backpack is still plenty of room!