Which Fizik? Why not just use the integrated mount if it's a Mistic/Tritone?

Its a Transiro Mistica Carbon SADDLE. What cage would you put with it?

This likely came with your saddle depending on where you bought it. The tab that sticks forward (towards the seapost) is threaded for a CO2 cartridge. An innertube can then be bungeed or velcroed using a cheap strap to the "valley" also on the seatpost side between the mount and the CO2. Similar to this. I recommend Gorilla XT cages for this purpose but if you're looking for a cheaper but reliable solution, use the Specialized Rib Cage

Very helpful, thanks!!

I’ve got a profile design RMP rear mount and I’ve been super happy. I removed the included profile design cage and used a Tririg kappa cage instead. Bottle isn’t going anywhere. It’s on my ISM PN 1.1 saddle so not sure if it fits yours.

zip ties or an actual mount?

I mounted the tririg cage on the rmp where the stock cage was.