Construction:
The hot water bottle cover is knit in the round using the magic loop method and worked from the bottom up. It features a large colorwork pattern and is finished with a ribbed cuff for a snug fit. This pattern is designed specifically for small hot water bottles with a 0.2l capacity and fits only this size:

https://www.frosch-shop.de/waermflaschen/mini-waermflasch...

Yarn:
Fingering yarn, for example: Jamieson & Smith 2ply Jumper Weight
(105m / 25g = 210m / 50g = 420m / 100g)

Quantity:
MC about 15 – 20g, CC about 5 – 10g