I was using this to carry snacks for me and power pack for my phone. about the right size for that, and a few other things, like thin gloves and hat. But the fact that it didn't keep rain out was a drag. The handlebar velcro had less than an inch of overlap when fastened around 31.8 handlebars, which made its hold a bit tenuous.
Use for longer days on bike. Used on a canceled century when I rode the route anyway - when hauling more food and rain jacket took up jersey pocket. Perfect for gravel bike when carrying larger spares. Fabric is stiff enough for bag to hold it shape. Attachments points are good. Zipper top is interfered with by Garmin mount but not a biggie. Back slip pocket is good for route maps. I cut off the hip belt - it is way over engineered and heavy. Too bad not detachable.
I used this bag on a two week bike touring trip, and it was the perfect size for my phone, wallet, first aid kit, and other essentials I wanted to get to quickly. Now I use it everday, on and off my bike, and I still love it.
It's not 100% waterproof, but I did find it water resistant.
The design is sturdy, functional, and beautiful. Love it!