The 031-70538-12G: It is rated to 12 GHz, which puts it well beyond the bandwidth needed for standard-definition video — this connector is sized for high-frequency broadband, HD-SDI broadcast, and instrumentation links where the 75 Ohm impedance path must be maintained cleanly through the interconnect. The kit ships as four pieces: the connector body, one center contact, one crimp ferrule, and one PTFE insulator. That means a single order code covers everything needed to terminate one cable end — no separate sourcing of the contact or ferrule.
This jack is specified for Belden 1855A and 4855R cables — both are 75 Ohm precision coax types with a solid or stranded center conductor and a foam or solid polyethylene dielectric. If you are terminating a different 75 Ohm cable with similar dielectric diameter and braid coverage, compare the cable group dimensions against the crimp tooling range before committing. That cycle life is typical for a BNC in test-equipment or patch-panel service where the connector sees regular reconnection; for a permanent install the gold plating is margin, not a limit.
The 034-1107-12G is the mating male plug for this jack — same 75 Ohm impedance, same 500-cycle rating, same Belden 1855A/4855R cable group, same bayonet lock interface. The difference is gender: the 031-70538-12G is a jack (female socket), the 034-1107-12G is a plug (male pin). If you are building a cable assembly, order one of each per mated pair. The 031-70558-12G is also a plug but specified for Belden 4694P cable — different dielectric dimensions, so the crimp ferrule and center contact may not match the 1855A cable group. Stick with the 034-1107-12G for this cable type.