What size of under saddle bag for gravel bike? 0.7L or 1L?

Hello, I am looking for a bag for my gravel bike to store a tube, multi tool, levers, patch kit, …
As I am shopping online it is hard to visualize and compare different size bags. I suspect I either need a medium size which seems to be about 0.7L or a large which seems to be 1L.
Any feedback would be greatly appreciated to ensure I get the right bag the first time as a return would be either a hassle or not possible.
Thanks very much.

Not sure how many liters the Castelli saddle bags are, but, I use the mini on both my Exploro and Strada. The Exploro has a 2” 650b tube, Specialized Emit 9 tool, standard Allen wrench for the axle, 20g cartridge and chuck, and a boot patch. With a a 700x28c tube, I can fit all that plus a second cartridge. If you want a second tube and second cartridge, go with the XL bag.


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Thank you, surprised all that can fit in there. I think the boxy shape of the bag must work better than the oblong ones.

https://amzn.to/35q1s5W This is the way roll.

Get a mini-frame bag - 2.5L -3l. too.

A full 1L bag sounds big to me but I only carry the minimum to fix tubeless flats, one tube, and a multi-tool.

I have a 0.8L saddle bag that is just about right.

It doesn’t fit my pump, but can fit everything else. I also use it for my MTB where the tube is bigger. So for just gravel, you could probably get by with 0.7L.