The M4 in the name stands for “Mark 4” and that’s how I’ll be referring to them in this review because there’s no easy way to say the name otherwise. One can’t refer to them as just ‘1000XM4’ because they might be confused with the WH-1000XM4 - Sony’s excellent over-the-ear headphones. Referring to them as the ‘WF’ also makes no sense. Anyway, Mark 4 it is!