Black Strip - for VC-S2 ALU or VC-E
White Strip - for VC-S, VC-S MK II, VC-S2 ALU or VC-E
Grey Strip - for VC-S MK II, but compatible with all models (thicker)

The Black Strip is not compatible with earlier VC-S and VC-S MK II vacuum arms, as they have a plastic cap that overlaps the depth covered by the black felt strips. These vacuum arms can only use the White or Grey Strips, which are deeper.