【Fleece Cover Hot Water Bottle】 - Design: Embroidered with a rabbit face - Color: Gray - Material: Soft fleece cover - Cap: Plastic cap - Size: 18cm wide, 28cm long I bought a lot of these as gifts for my family, but they don't use hot water bottles, so these are unused. I use a different pattern myself. I fill it with about 80-degree Celsius water, about 80% full. When used for 8 hours of sleep, the warmth is considerably reduced in the morning, but it stays warm enough for about 4-5 hours, which is sufficient for sleeping. I like that it has a pocket to put your hands in and the material is soft.