Was looking for a road bike waterproof bag with a small profile to attach on the toptube of my road bike to hold my phone, keys, and a power bar or two and this Topeak Dry Bag has worked great for that purpose. This dry bag is built very well: the sides have some structure to them so they don't flex while cycling and the zipper is water tight as long as you push the zipper into the sleeve/cover at the top of the bag making it fully zipped. The zipper also doesn't flap in the wind while riding when secured in the sleeve/cover. I've ridden in light rain and brief down-pours with this dry bag and everything inside stayed 100% dry. If there is water beaded-up on it before you unzip it to retrieve your phone, keys, snacks, or other stored items, obviously the water will get into the compartment so keep that in mind and wipe the water off first before unzipping it. I haven't had any issues with the dry bag swaying from side to side while riding, but if you fill it up with things, making it heavy, be sure to really tighten-down the velcro straps, which, are very secure when installed correctly. The dry bag, when completely full, will move slightly to one side or the other, but it's minimal movement and not distracting while riding. And, I've never worried about the bag falling off. I've yanked on it a few times, pulling it up and side to side while riding just to test it, and the straps stayed secured with no loosening.Space-wise, I can fit my iPhone 8 (in a leather wallet or waterproof case), upright only in this dry bag, as well as my keys, and two Lara Bars. The fit is tight, but it works for what I wanted it to carry. For reference, I use this dry bag on a 2004 Felt F70 Racer road bike and it fits the frame very well by attaching one of the straps to the toptube and the other to the base of the handlebar stem.The only reason I've given this bag 4 stars instead of 5 is I wish it had included a few more extra strap options of varying length. This bag seems to work best on road bikes; the frame on my full-suspension mtn bike is too thick to work securely with the included straps.