It is a polyamide (PA) nylon body component — not a connector itself, but the hardware that secures the jack to a panel or chassis. The bushing provides the mechanical interface between the jack and the panel cutout, centering the connector and taking up the clearance around the mounting hole.
This bushing is intended for use with TE Connectivity BNC jacks — the female panel-mount or bulkhead side of a BNC interconnect. It is not a universal fit for all BNC connectors; compatibility is limited to jacks that share the Coaxicon series mounting geometry. The polyamide body provides electrical isolation between the jack shell and the panel, useful when the panel is grounded and the jack needs to float, or when a non-conductive mounting is required.