I wanted an easy on/off bag big enough to hold all my stuff. This bag clips into a separate mounting bracket attached to the saddle. Easy one handed removal and replacement. Sturdy, will not accidentally fall off. I carry a gravel sized tube, CO2 inflator and spare cartridge, tire levers, disk brake removal tool, hex wrench multi tool, and a small cable lock with room to spare. The bag does not have a zipper closure. It's waterproof. The opening folds over and is secured by two elastic straps on either side. I have broken a few closure zippers in the past. This is a much better way to secure the opening. It's waterproof. I have never owned a waterproof saddle bag!
I now run the Burrito Pack on multiple bikes. It can fit a tubolito tube (29-inch mtb or 700C gravel), 2 pedros tire levers, multi-tool, 2 co2's (16oz or 20oz) with valve, and a pack of extra hardware with room to spare. All while still being tight and compact. I also really like when you have it off and unfolded, you actually get a pretty big surface to set small parts on. On the mtb's it is great how it does not interfere with the dropper post and doesn't touch the post at all.
Good pack, about the right size. Deeper than wide so you will need to be reaching down a relatively narrow bag to get to stuff at the bottom. The top closure works great and it is comfortable. There is a laptop pocket that hangs on the inside along the back which I wish it had more pockets/compartments since the pack is otherwise pocketless. Perfectly waterproof so far. The pack is very reflective and high vis during the day so it helps in preventing me from being run over (or so I tell myself). Like everything else I own, the surface of the bag does collect dirt which diminishes its reflectivity a little. I haven't tried washing it yet, but it does seem like it would be a little harder to clean than the regular, smooth bags that are not reflective.
I agree with the reviews that complain about the pack shifting or even coming open during a ride. I had this problem for the first couple of weeks. I finally figured out that I needed to pack it with the bare minimum--two CO2 cartridges with one connected to nozzle, one tube (700cx28), one Parktool tire lever, one Parktool GP-2 patch kit, one Parktool I-Beam mini tool. Arrange all contents into roll as flatly as possible. Fold roll loosely so that the both side of the velcro strap line up exactly. When securing to seat rails, ensure that the velcro strap and the padding used for the BOA wire are pressed together. The friction between the two surfaces is key to keeping roll fixed in place when riding. Once I figured this out, I had no problems but feel Silca should have given these instructions rather than learning through trial and error. This should make sense if you give it a try.