⭐️ Both items have been used a few times, thoroughly hand-washed, and stored at home. ⭐️ The gray one's included USB charging unit is broken, so there is no charging unit. It functions normally otherwise, but I don't know if it can be heated without the charging unit. The size is also adjustable. ⭐️ How about it for those who work night shifts or have irregular work schedules and need to sleep during the day? I think there are other uses as well, so please consider it. ⭐️ The black one also has Velcro, so it's adjustable. ⭐️ Please understand that these are used items before purchasing. The length can be seen in the photos, and you can get an approximate size. The reason I marked them as having some scratches and dirt is because the gray one's charging unit is missing. ⭐️ Please feel free to comment if you have any questions. Also, please note that I will prioritize the person who makes an immediate purchase, even if there are comments.