I used this to keep an ice cream cake cold when I bought it from 31 Ice Cream. I've only used it to bring the cake home from the store! It's been folded up and stored at home for a long time as shown in the photos, so I hope you understand. m(_ _)m It's approximately 25cm square! I will fold it up as much as possible and put it in an envelope to ship via Yu-Yu Mercari mail, which will be dropped off in a post box! Thank you for your understanding and consideration!