・Useful when backpack shoulder straps are too long. ・See photo ③ for the inner diameter. ・Shipped at the lowest possible cost (scheduled to be sent via regular mail). (Note) Photo ④ is an example of how it's used (image provided). Please check photo ④ for the mounting image. The inner diameter of the rubber band cannot be adjusted. In the case of a covert case, the straps are thin, so the inner diameter is a bit large, and it's attached at the top like in the photo.