MUJI Neck Cooler M Size (Gray) Brand: MUJI [Product Information] Product Name: Neck Cooler External Dimensions: 14 x 16cm (M Size) When the inside is solidified and placed around the neck, you'll feel a cool sensation. To solidify the inside: ・Cool in the refrigerator for 20 minutes or more in a flat state. ・Cool in the freezer for 5 minutes or more. ・Cool in an environment below 28°C, such as cold water (the lower the temperature, the faster it solidifies). Even if the cool sensation disappears after use, you can use it repeatedly by solidifying the inside again using the methods above. Furthermore, if you use this with a certain product, you can incorporate it as part of your coordination.