Thank you for viewing! This is a chest belt with adjustable length, using Velcro. Chest belts are used to secure the shoulder straps of a backpack in front of the chest, preventing them from slipping. [Reference] Fits total lengths of 21cm to 30cm (Assuming a belt width of 2.5cm) Fits total lengths of 21cm to 27cm (Assuming a belt width of 5cm) This is made for young children who cannot yet use buckles. Velcro is safe! And they can easily put it on and take it off themselves with a "peel-off" sound ♡ Recently, I've heard that some kindergartens are specifying Velcro-type chest belts. My child went to daycare, and for field trips, they required backpacks with chest belts. Commercially available backpacks, even for babies, usually have buckle types, right?? I was worried about fingers getting caught, so I used this Velcro type until my child was about 4 years old. Thanks to this, many children are using it.