I ride mostly gravel events and have tried various storage solutions for all-day nutrition. My issue with bags I've tried were related to how secure it was on the frame (i.e. wobbly vs stationary), capacity, how easy it was to open/close whilst riding, and how hard it was on my frame (I don't have top tube rivets so straps are my only option). This bag ticked all the boxes: easy to attach and sits securely even during the washboard gravel sections, easy to access, and the frame paint is not affected. And, it's very lightweight!
I've had this pack for about 3 years now, and put it through hell. No issues. Those saying you can't fit a spare / levers / multitool / co2... yes you can; it is possible. It's not roomy by any means, but as long as you carefully pick what you put in the pack, you're good. Keep things flat. For road rides I keep the following: 32-42 butyl spare, one Pedros lever, one much thinner ProBike lever, one Silca Italian army knife, one 20g co2 w/inflator, one Park patch kit, one nitrile glove and one small microfiber rag. Few band-aids. For gravel rides I just stuff the Dynaplug pill in there - and it also fits (tightly). Almost everybody I ride with has this seat pack, it's kind of the standard these days. Worth the extra coin.
This seat pack is perfect for the road cyclist that wants a minimalist flat kit and nothing more. Its everything it needs to be and doesn't overcomplicate (i.e. silca mattone). Fits a TPU tube, tire lever, 16g CO2 w/ head, tire boot, and small mini tool perfectly. Quality construction and I like the wider velcro strap. Can't beat it for the price. Looks clean on the bike- nice not heaving a seatpost strap.
(*would be too small for a regular butyl gravel size tube and accessories)
Was reluctant to spend the money on this saddle bag, but I was going on a trip that required riding 100 miles per day for 7 days. I usually just carry a Dyna Plug and my small battery operated pump with me, but based on the fact that these rides were un supported and there was no available services for most of them I decided to get the bag. It worked out great. I was able to put my small multitool, a co2 cartridge, a mini pump hose and my dynamite plug kit. Turns out I had to use it twice. Once for a friend and once for myself. Highly recommend this product.