In UK and they come with a barrel to accept a 2.5mm pin, which is wrong. (too tight)
The Mbox 3 pro has a 2.8mm pin on its housing
INPUT: 100-240V, 50/60Hz, 1.5A OUTPUT: 9V, 4000mA, 36VA
Note its also a 4amp (4000ma) output
So i had to get a barrel with an inner 2.8mm hole, to replace/solder the 2.5mm one. Cant recall the outer barrel size but I think 5.5mm is correct.
https://duc.avid.com/showthread.php?t=380242