Glass beads provide the transition from a connector, through a housing wall, to a microcircuit. The V100B bead also provides hermeticity* to protect a module's internal circuitry from harsh external environments. The V100B is designed to work with these V connectors: V102F, V102M, V103F, and V103M. Anritsu also sells the V100 Glass Bead. The difference between the V100 and the V100B is that only the V100B is specified to be hermetic. The V100 and V100B are dimensionally identical.
*Glass Bead Hermeticity Spec: Hermetic to 1 x 10-8 std cc He/sec at 1atm differential