My Osprey Nato 58 canteen does not fit in my Crusader stainless steel mug, in that the canteen is too large to nest in this SS mug. Either the canteen is too large in diameter or the mug is too small. Its a shame because if they fit, this would be an excellent system.

Also, I have another Osprey Nato 58 canteen where the Osprey Nato plastic cup is much too loose to positively snap on to the canteen.

My guess is the Osprey Nato 58 canteens are not even close to being uniform in specs. There's about an 8% difference as to how much water my two Nato Osprey 58 canteens hold. Others have commented on this as well. The Osprey label info that's printed on the side of these two canteens is precisely the same.

Does Nato accept all the non-standard capacities and sizes? or are these Osprey 58 canteens the Nato rejects?