I've been using the ROCKBROS Top Tube Bike Bag for a few weeks now, and here's my honest take. First off, the EVA shell is *legit*—no crushing or sagging, even when stuffed with tools. It feels like a tiny armored tank strapped to my bike frame.

The water-resistant PU material saved my phone during a surprise drizzle, though I wouldn’t trust it in a downpour (the double zippers are tight but not submerge-proof). Installation? A breeze with the three hook-and-loop straps—it hasn’t budged on bumpy trails.

But here’s the catch: SIZE MATTERS. The "large" version barely fits my iPhone 13 Pro Max *without* a case. Wallet + keys? Forget it. If you’re packing slim (energy gels, multitool), it’s perfect. Knees hitting the bag? Only if you’re tall or ride aggressively—I adjusted the angle and it cleared.

Verdict: Great for minimalist riders who prioritize durability over space. If you need room for a sandwich-sized haul, look elsewhere. At $30-ish, it’s pricey for what it holds, but that EVA shell justifies the cost for rough terrains.