I have been a real convert to fidlock bottles since giving up on packs and have got the mounts on all but one of my bikes. However I have discovered the drawback. While I have never lost one from a bike , I managed to leave one on a wall while loading bike into car. You can get replacement bottles but they assume you can transfer the magnetic bit from the old bottle to the new. Mine of course is still on the wall with the bottle. So I have had to buy a complete kit which is much amusing my riding chums who have found the fidlock a step too far !
They're brilliant. Bounced up to the top of Dyfi on the uplift trailers no problem.
You can buy the Twist bottles with or without the magnetic attachment built in IIRC. The ones with cost more than twice as much… which is why they sell the ones without… for a cheaper fix for people wanting to replace bottles that are old rather than lost.