Thank you for viewing! This is an adjustable "Velcro" chest belt. Chest belt → This belt fastens in front of the chest to prevent the shoulder straps of a backpack from slipping. [Reference] You can adjust it to fit the width of the backpack's shoulder straps. I think the maximum adjustment is about 7cm, as shown in the photo. It's made for young children who can't yet use buckles. With Velcro, it's safe! And they can take it on and off themselves with a "peel-peel" sound ♡ Recently, I've heard that some kindergartens are specifying Velcro-type chest belts. My child went to daycare, so they required a "backpack with a chest belt" for field trips. Commercially available ones are usually buckle-type, even for baby backpacks, right?? I was worried about pinching fingers, so I used this Velcro type until my child was about 4 years old. Thanks to that, many children are using it.