It serves as the outer shell piece that compresses over the cable braid and inner ferrule during crimping, providing strain relief and shielding continuity for cable entries sized for DB15 through DB50 connector shells.
What it fits and where it goes
This ferrule is used with AMPLIMITE Series D-Sub connectors and accepts cable diameters that correspond to shell sizes from 15 positions up to 50 positions. It is the outer ferrule, not the inner ferrule: the inner piece sits against the cable jacket, and this outer ferrule crimps over it to lock the braid and jacket in place inside the backshell.