Attached whistle for emergent situations
Available on any backpack with the tape on shoulder straps shown below:
Adjustable length with front buckle.
Length: 14-33 cm; Width: 2 cm
Avoiding backpack's shoulder strap slipping off and wobbling of backpack while walking.
Increase instability while carrying your bag.
Intensely-weaved nylon belt + reinforced POM buckle:
Highly resistant and durable.
How to attach the buckle belt on your backpack: