Part Number Difference A-B

What is the difference between these 2 units?
XE3-4X00A00-US and XE3-4X00B00-US

Change in casing or antennas or anything? Or does B mean like rev 2?

@Springs this is a Hardware Revision change. It could be anything Cambium wants to track internally, for e.g. a factory change, change in some components etc. No functional change.