I have the Lezyne M-Caddy QR on both my road and CX/Gravel bike. I love the quick release so I don't have to fiddle with straps and worry about rubbing on the seat post. It holds the necessary gear: co2 holder, extra cartridges, mini-tool, tubeless darts, cash, quick link tool and I forget what all else. Pretty much all I need to not be stranded by the side of the road. It also leaves plenty of space for a light mount, in this case, a Garmin Varia. It would be nice if I could have just a single bag and buy multiple mounts for the saddle, but such is life.