They sell defective backpack.
I bought the 35L new backpack. The zipper has a zipper problem. It strips out the surrounding on the hard shell area. When I informed the customer service they acted like they would help. But I have to ship the product again and pay tax again in my country. Poor workmanship from Ulanzi. I would not recommend this backpack as it feels cheap. Customer service does not act according to a broader perspective. Go for another brand. DISAPPOINTED!