This reusable, eco-friendly heat storage water bottle provides up to 8 hours of warmth with just 10 minutes of heating. - Product Name: Heat Storage Hot Water Bag - Size: Approximately 30 x 33 x 3 cm - Electricity Cost: Approximately ¥2.1 per use, ¥63 per month (based on 30 days) - Heat Retention Time: Up to approximately 8 hours - How to Use: Heats in approximately 10 minutes for up to 8 hours of warmth - Features: Reusable, eco-friendly heat storage water bottle I bought this last year but haven't used it.