Isn't that MEXAS armour a non-explosive reactive armour?
My understanding of NERA is that it's basically the same as ERA, but the explosive is replaced by a fast-reacting polymer whose volume inceases massively when subjected to heat. This has the effect of throwing the outer plate towards the HEAT warhead in the same way as ERA, thus spoiling it's stand-off distance (stand-off distance is critical for shaped charges to work properly)
EDIT : no, MEXAS is a ceramic composite, not a NERA. Must have been thinking of something else.....