A few years ago, I purchased this rare, red ceramic hot water bottle made by Yamacho Seito from the Gaia Project. It's designed to retain warmth for a long time. - Color: Red - Shape: Oval - Material: Ceramic - Design: Ribbed - Bottom: Smooth finish When using, fill with hot water up to 80% of its capacity. Filling it completely may cause it to crack due to expansion. Also, the body becomes hot after filling with hot water, so be sure to tighten the stopper securely and carry it wrapped in a large towel or similar. Putting it in your futon about 30 minutes before bed will create a warm and cozy feeling, enveloping you in happiness (* 'ᵕ' )☆ Thank you for looking.