Nice bag! It has a large velcro to hold the mobile, and the truth is it looks good and doesn't move. To hold it to the handlebar has three velcros. The mobile screen responds well. 100% recommended.
It's a very rigid and good quality backpack. I haven't tried it yet, I'll have to see if it's water resistant, rain. It's very spacious you can carry your phone, house keys, tools and more