There are around ten million threads in this subject, here is all you need to know-
Anything up to 600 litre tank.
Be aware of max weight over rear axle.
Those that have them, love them.
Everyone else thinks they are either pikey, too small, too thirsty, will be nicked for ram raiding or you may even go to hell if you buy one.
I think they are great for wfp but could limit you if you expand and can't get home to refill with water.