SUO 28°ICE COOL Ruck2 Purchased about 3 years ago and used 2-3 times in the same year. I tend to use the neck ring more, so I've decided to part with this. It has been washed with detergent. The straps for attachment have not been washed. There are no scratches, tears, or noticeable stains. I can't say for sure without comparing it to a new one, but I think there is some slight yellowing overall. I would appreciate it if you don't mind. Quoted from the official website: Top width: approx. 19cm Height: approx. 31cm Bottom width: approx. 25cm Weight: 360±15g SUO 28°ICE COOL Ruck2 Collection. From the SUO ICE series, a backpack type has arrived that attaches to your backpack to cool your sweaty back. The SUO ICE series is an innovative product that utilizes organic and natural plant-based PCM (Phase Change Material). This product has the property of freezing and melting according to the temperature environment, absorbing and releasing heat. As a result, it quickly and efficiently regulates body temperature, providing comfortable cooling. Because it uses organic materials, it is environmentally friendly and highly safe. It has a specific gravity about 30% lighter than water, making it easy to handle and safe to use repeatedly. Attach it to your backpack to efficiently cool your entire body. It gently cools the body with a moderate cool temperature, reducing the risk of heatstroke. Also, it is divided into blocks, so the liquid does not shift, providing even cooling effect throughout. [Difference between 256 and 28°] ・28° is not too cold, providing a comfortable, soft coolness and naturally freezes at 26-28°C or below. ・The 256 type is slightly cooler than 28° and naturally freezes at 24-25°C or below.